Alignment analysis

[ADAM]

So took the car in for an alignment (should have done this sooner)
here is what we got...

before alignment

front left toe -0.04"
front right toe -0.05"

front left camber -4.39
front right camber -4.35

rear left toe -0.13"
rear right toe -0.26"

rear left camber -2.36
rear right camber -2.16

looks like the rear had way to much rear toe out..what would that do to the car? could that be my understeering issue?

anyway I took Krispy's suggested settings and this is after the alignment..and got the rear toe into some toe in now

camber left all the same...since rear is maxed out in its stock settings and front should be ok with -4.3

after alignment

front left toe -0.06"
front right toe -0.05"


rear left toe +0.02"
rear right toe +0.01"


comments....suggestions?


Adam

[Tashko]

Hmm, I've always used toe-out in the front to aid turn-in and toe-out in the back to help rotation. This is on an AWD so maybe RWD is different.

It may also depend on how your toe changes with compression/rebound and camber change where you want to set the static values.

[ADAM]

I do have toe out in the front now...and toe in the rear

[ScotcH]

Toe out in the rear would induce poweron oversteer, so that is definitely not your understeer problem. The new settings sound good.

[Cap'n Pete]

Hmm, I've always used toe-out in the front to aid turn-in and toe-out in the back to help rotation. This is on an AWD so maybe RWD is different.
Makes perfect sense.

I do have toe out in the front now...and toe in the rear
No you don't, and no you don't ...

... unless you're doing "double negative" math? :rolleyes: "+" toe is toe-out. "-" toe is toe-in.

So according to all of your figures, you HAD and still HAVE toe-in in the front, while you did change the back from being toe-in before, to toe-out now.

before alignment

front left toe -0.04"
front right toe -0.05"

rear left toe -0.13"
rear right toe -0.26"

after alignment

front left toe -0.06"
front right toe -0.05"

rear left toe +0.02"
rear right toe +0.01"

The toe-out in the rear should, like Tashko said, help the rear end rotate. It's not a lot of toe-out, so to what extent? Guess you'll find out. But in the front, you actually gave yourself and additional .02" of total toe-in (-.06" + -.05" = -.11", which is not far from -.125", which is -1/8"). If you want toe-out, you'd be looking for +.xx".

[ADAM]

no they actually reverse what common sense would be on the alignment machines printouts... they consider a - to be toe out ...and a + to be toe in


I asked the tech guy at the shop 3 times to make sure..that he in fact was adding toe out to the front which shows as - , and adding toe in on the rear which shows as +

not sure why they do this maybe they consider it an adjustment to the back of the wheel which in that case they are adding or subtracting from dead straight?

anyone know why they do that with alignment?

[ScotcH]

Just check it with a couple of boards and 2 tape measures to be sure.

I'm not sure about othe RWD cars, but on a BMW, having rear toe-out basically makes the car undrivable. You just NEVER want rear toe-out.

[ADAM]

not even on the front?

I can 100% see why not on the rear

[ScotcH]

not even on the front?

I can 100% see why not on the rear

Sorry ... I meant on the rear. Yes, you can have some tow out in front to help turn in. Too much might give you mid-corner push though.

[Cap'n Pete]

no they actually reverse what common sense would be on the alignment machines printouts... they consider a - to be toe out ...and a + to be toe in


I asked the tech guy at the shop 3 times to make sure..that he in fact was adding toe out to the front which shows as - , and adding toe in on the rear which shows as +
Ok then ... so it's like I said ... "double negative" :rolleyes:.

Basically, their machine is telling you how much toe-in you have. Anything greater than 0 is toe-in (+) and anything less than 0 is toe-out (-).

So -.06" of toe-in is +.06" of toe-out!! ..... weird, but if that's how it is, then that's how it is!!! :cool:

Then you can ignore the part where I said you don't have toe-out!! :p

(FWIW, the alignment shop I went to, the computer displayed toe-in as "-" and toe-out as "+", and everywhere I've seen it discussed, that's the way it's been).

[Slowpoke]

Hmm! Man Adam, with settings like those, I would have thought that thing would have turned like crazy with some trail braking, especially from mid-corner onwards. Is it unstable under braking? What hot pressures do you use front to rear?

Perhaps with those wide wheels, you might need to dial back more on Front Camber still to get more tire on the ground for cornering. Tire temperatures or wear should tell you that.

For autoslalom I like a little toe out up front. 2/16" or ~0.13" Total (0.065 a side). But for the track, I prefer the confidence and predictability of 0.0 toe. If the car pushes from the apex onwards I add up to 2/16" toe out in the rear for rotation. Some folks like more than that.

You're using 10kg front, 8kg rear, with McPherson struts front and rear, right? Your weight balance was near 50/50, front to rear, wasn't it? Perhaps some more rear spring?

[Ron]

You just NEVER want rear toe-out.

unless you are Zanardi at the end of a race!

[James Mewett]

According to Millikan (Race Car Vehicle Dynamics), a typical radial tire produces a side force due to camber approximately equal to the side force due to steer at 1/10th the camber angle. This tells me that negative camber is stabilizing for the same reason that toe in is stabilizing, and that toe out (in degrees) equal to 1/10th of negative camber angle should not cause instability issues. This means that at -2.5° negative camber, 0.25° of toe out (which coincidentally corresponds to about 0.25" of total toe out on a typical tire) is not unreasonable. I have tried more without serious consequences. The same thinking may be applicable rear toe, but conventional wisdom says that toe out at the rear will cause instability (oversteer) at track speeds so I haven't experimented with this.

Most references are very reluctant to suggest toe out, and Millikan is the only author I have seen to point out the camber/steer relationship. Perhaps they are paranoid about liability. In any case, only experimentation will yield the definitive answer for your situation.

I suggest much more front toe out. With -4 degrees front camber, try up to 0.4" total toe out (0.2" per side).

[ADAM]

hnmmm even more toe out..

well somethings gotta change cause the nose is just plowing..


maybe the front splitter will be the answer..will see

[Pete@Marcor]

What kind of tire temperatures are you running?

I am not surprised you induced more understeer with your new alignment settings. however, this probably makes it more consistent. The virtually 0 toe in the back is a good start.

But, recently, you have gone from a large aftermarket rear bar to either no rear bar to a small OE one. This would shift the balance of roll stiffness towards the front. Now, you have taken a fair amount of rear toe out away from the car, making the car less loose.

Why are you averse to changing spring rates?

Where in the corner is your car understeering?

[Pete@Marcor]

I suggest much more front toe out. With -4 degrees front camber, try up to 0.4" total toe out (0.2" per side).

Oh, and I think that this is way too much front toe. After about .25" total toe out, cars tend to slow down, as the front tires are just scrubbing.

Realistically all of this discussing is just a prelude to what you really need to do, which is test, and try different setups and changing parts. Change springs, and see what happens, etc...

[Chris P]

What kind of tire temperatures are you running?

I am not surprised you induced more understeer with your new alignment settings. however, this probably makes it more consistent. The virtually 0 toe in the back is a good start.

But, recently, you have gone from a large aftermarket rear bar to either no rear bar to a small OE one. This would shift the balance of roll stiffness towards the front. Now, you have taken a fair amount of rear toe out away from the car, making the car less loose.

Why are you averse to changing spring rates?

Where in the corner is your car understeering?


he hasn't tried the new alignment settings yet. Basically, I just gave him baseline figures (the new specs) and told him to test. :)

Adam is running some mild HP numbers (~350hp) and also considering his driving style, a little rear toe-in is a good starting place apposed to zero.

[James Mewett]

Oh, and I think that this is way too much front toe. After about .25" total toe out, cars tend to slow down, as the front tires are just scrubbing.

I think what "Millikan Rule" tells us is that to avoid scrubbing, you must toe out a negatively cambered tire by 1/10th the camber angle (when toe is expressed as an angle). You need to do that to get rid of the camber thrust (side force generated by camber) and presumably a tire that generates no side force is not scrubbing.

Given that -2.5° front camber is a pretty normal setting, your rule of thumb may be generally true though.

[ADAM]

yeah... its gonna take more nitty gritty testing and tuning which I hate...

however I might have some crazy aero testing in the works :)

war of escalation type stuff....

he he...since the rules dont call out points for a front wing :)

[MazdaMatt]

Adam, it is recommended that you remove all aero gear and test and tune your alignment in low-speed turns. When your car is perfectly balanced and predictable and how you want it, THEN put your aero gear on and tackle the high-speed turns to balance out your aero gear.

[ADAM]

yeah it will be removeable stuff

[Pete@Marcor]

I think what "Millikan Rule" tells us is that to avoid scrubbing, you must toe out a negatively cambered tire by 1/10th the camber angle (when toe is expressed as an angle). You need to do that to get rid of the camber thrust (side force generated by camber) and presumably a tire that generates no side force is not scrubbing.

Given that -2.5° front camber is a pretty normal setting, your rule of thumb may be generally true though.

Yes, but at 2.5 degrees of negative camber, that still would be .5" of total toe, unless you are talking about taking the number of degrees for the camber, and relating it to the angle of toe:

1/8" = 0.348 degrees (total, so 0.174 degrees per side)
7/64" = 0.304 degrees (0.152 per side)
3/32 = 0.26 degrees (0.13 per side)
5/64 = 0.218 degrees (0.109 per side)
1/16" = 0.174 degrees (0.87 per side)
3/64" = 0.13 degrees (0.065 per side)
1/32" = 0.087 degrees (0.0435 per side)
1/64" = 0.0435 degrees (0.02175 per side)
(above for a 24.3" tire)

If so, then 3.5 degress of camber would require 1/8" per side to equalize the thrust on it, which puts the settings more in the realm of likelihood.

I still don't know how the front camber is so high, though. The car is stiff enough that it should not be falling off of the tire that much.

[ADAM]

I can reduce the front camber easy Pete...I have good control over it..I can go from +2 to about -7 with my camber plates..

I just keep it at -4 cause historically thats what I have run without issues...I have tried from-2 to -6 this season, and it does not really help my understeer issue...

[Pete@Marcor]

I can reduce the front camber easy Pete...I have good control over it..I can go from +2 to about -7 with my camber plates..

I just keep it at -4 cause historically thats what I have run without issues...I have tried from-2 to -6 this season, and it does not really help my understeer issue...

You REALLY need to do some tire temp readings, to see if you are in the ball park. I would think you should be in the 2.5-3 degree range, 1/8" toe out in the front, with some camber out back and 0 to a tiny bit of toe in in the back.

Why did you run -4 degrees?

[James Mewett]

Yes, but at 2.5 degrees of negative camber, that still would be .5" of total toe, unless you are talking about taking the number of degrees for the camber, and relating it to the angle of toe:

1/8" = 0.348 degrees (total, so 0.174 degrees per side)


I am treating each tire individually, so at 3.5 degrees negative camber each tire should toe out 0.35 degrees from straight ahead to eliminate any scrubbing. This corresponds to a total toe in inches of:

2 x 24.3 inches x Sine (0.35 degrees) = 0.30 inches total toe out

or 0.15" per side.

I hope this is clearer.

[ADAM]

at -4 car seemed to like it in the past..made the car very nuetral in the corners...

[bsclywilly]

I think what "Millikan Rule" tells us is that to avoid scrubbing, you must toe out a negatively cambered tire by 1/10th the camber angle (when toe is expressed as an angle). You need to do that to get rid of the camber thrust (side force generated by camber) and presumably a tire that generates no side force is not scrubbing.

Given that -2.5° front camber is a pretty normal setting, your rule of thumb may be generally true though.

James, that statement is not accurate. Milliken describes camber thrust to having a similar affect as toe, that being, they both generate lateral force (rcvd p46,726). But it does not mean that a cambered tire is 'scrubbing'. Haney (tire p110)states that the lateral force produced by camber thrust does not result in a significant increase in tire temperatures which suggests there is little scrub. When you counteract the camber induced lateral force with a slip angle (toe), then you are creating scrubbing/increased temps/increased wear. This applies to daily driving too, the wear associated with having cambered tires is significantly less than having even 0.3deg total toe.

Think of it as camber thrust causes the tread to move side to side. Toe causes the tread to twist when it comes in contact with the road.

edit: and yes, you can have scrubbing even if there is zero lateral force.

[jonweir]

James, that statement is not accurate. Milliken describes camber thrust to having a similar affect as toe, that being, they both generate lateral force (rcvd p46,726). But it does not mean that a cambered tire is 'scrubbing'. Haney (tire p110)states that the lateral force produced by camber thrust does not result in a significant increase in tire temperatures which suggests there is little scrub. When you counteract the camber induced lateral force with a slip angle (toe), then you are creating scrubbing/increased temps/increased wear. This applies to daily driving too, the wear associated with having cambered tires is significantly less than having even 0.3deg total toe.

Think of it as camber thrust causes the tread to move side to side. Toe causes the tread to twist when it comes in contact with the road.

edit: and yes, you can have scrubbing even if there is zero lateral force.

Hey, is this FSAE.com? :p

But seriously, excellent clarification Will.

[James Mewett]

Yes, you can have scrubbing even if there is zero lateral force.

That is really interesting, but I am not sure that your conclusion regarding wear naturally follows. Absent camber, a tire with 0.3 degrees of toe has a slip angle of 0.3 degrees when travelling straight. That isn't much (given that maximum lateral force won't occur until at least 20 times that value), and I doubt it would generate much heating either. "Scrubbing" seems to imply a literal scraping across the ground, which of course doesn't actually happen. Slip angle is largely an elastic phenomenon with little actual sliding in the contact patch at low slip angles.

Thus I would say that yes, you can have slip angle without sliding ("scrubbing") in the contact patch, then toe won't necessarily result in excessive wear. It may be that the excessive wear we often see on cambered cars is precisely because they don't have enough toe out. Of course, this is speculation on my part. Your theory seems just as speculative though ...

[Pete@Marcor]

That is really interesting, but I am not sure that your conclusion regarding wear naturally follows. Absent camber, a tire with 0.3 degrees of toe has a slip angle of 0.3 degrees when travelling straight. That isn't much (given that maximum lateral force won't occur until at least 20 times that value), and I doubt it would generate much heating either. "Scrubbing" seems to imply a literal scraping across the ground, which of course doesn't actually happen.

James, put 7/32" of total toe (almost 1/4") in your car, and see how fast your tires wear. :-)

[philip_240sx]

Adam, what (if any) effect has the LS1 install changed the suspension geometry. Were there not subframe and tension rod mounting spacers installed?

[ADAM]

well it shifted the weight by 2% more to the nose...since the engine and tranny are heavier than the 4cyl overall

and the spacers used to fit the whole thing into the car lifted the nose by 1/2inch

other than that the whole thing is the same..

[Do It Sidewayz]

and the spacers used to fit the whole thing into the car lifted the nose by 1/2inch



Either drop the front back down that 1/2" or raise the back.

[ScotcH]

Either drop the front back down that 1/2" or raise the back.

Yup ... rake has a huge effect on handling.

[ADAM]

will do that as well...since its an easy change with the coilovers

[philip_240sx]

I was referring to the fact the subframe spacers have changed the mounting locations of the lower control arms and TC rod lowering them by 1/2". By lowering them, you may have affected the suspension geometry ie. camber curve, kingpin angle, etc. IIRC you gained a large amount of positive camber once everything was installed. To compensate, you had to use some additional camber correction bolts, etc.

[ADAM]

yes thats a good point too... but I cant change that other wise the engine cant fit into the car :)

maybe If I got some of those adjustable suspension arms for the front? I know they make TC rods that adjust

what would I try and correct though?

the car seems to be acting the same as before just more understeer would changing the TC rod angle do that?

ohh the reason I gained all that positive camber was that the cam bolt was turned full positive..vs the usual setting of full negative..now I can just adjust the camber via the top plates

[JoeT]

Have you done any measurements to your current roll center as well? Since the CG is higher, the relationship to the roll center needs to be identified as well. The greater gap between the Roll Center and the C of G will change handling dynamics for sure, as well.

In addition to that, like PHil240 mentioned, you'll need to check your suspension geometry, I believe you use a front Mac Strut, right? So you'd need to check your camber curve to see if you're too low for the current suspension geometry, or you'll need to get a roll center correction kit of some sort.

[philip_240sx]

maybe If I got some of those adjustable suspension arms for the front? I know they make TC rods that adjust

what would I try and correct though?


Adjustable TC rods are used for caster adjustment.

http://splparts.com/main4/parts/NissanShared/Suspension/Multilink/SPLTensionRodBlue.jpg
image courtesy splparts.com

Adjustable lower control arms are used to change the roll centre.

http://splparts.com/main4/parts/NissanShared/Suspension/Multilink/SPLFrontLowerArm.jpg
image courtesy splparts.com


IIRC you have spacers for both the subframe (which has mounting points for the lower control arms and steering rack) and the TC rods (also part of the lower control arm). So the only dimension that has changed is the distance between the lower control arm assembly (including the knuckle) and the upper strut mount. I imagine this has changed the camber curve and caster slightly. I'm still not sure how much an effect this would be. Here is a sketch of the 240SX front suspension for reference:

http://splparts.com/main4/parts/S13/Suspension/Multilink/FrontSuspension.jpg
image courtesy splparts.com

[max attack]

So how do you adjust the roll center with those lower arms?,track width for sure.Is the inner pivot changed from the factory arm?.

My strut front car had the same issue with poor camber curve/low front roll center just due to fairly extreme lowering,I simply relocated the inner pivot up to correct.

[bsclywilly]

So how do you adjust the roll center with those lower arms?,track width for sure.Is the inner pivot changed from the factory arm?.

My strut front car had the same issue with poor camber curve/low front roll center just due to fairly extreme lowering,I simply relocated the inner pivot up to correct.

There are spacers above and below the spherical bearing that can be changed to raise or lower that ball joint. the threaded end is for adjusting camber (which will affect the track a small amount).

[max attack]

There are spacers above and below the spherical bearing that can be changed to raise or lower that ball joint. the threaded end is for adjusting camber (which will affect the track a small amount).


Really?,bizzaro.

The range wouldn't likely be noticable imo,my guess is that the rc is out a fair bit with the lowered suspension combined with the relocated crossmember.I was able to move my inner end up 1.5" combined with a 40mm roll center adjuster(spacer between the arm and spindle)which puts it back close to stock.

[Dave Barker]

Adam

No toe out in the rear

Use less front camber,try neg 3.0. Your brakes will work better and initial turn in should be better.

Don't know diddly about rear camber but wish I could have some.

I wouldn't use a ton of front toe out, it is more useful for Autox and isn't going to help braking stability (Toe out usually becomes higher as wgt transfers forward unless your tie rods connect at the back of the knuckle)

[bsclywilly]

Really?,bizzaro.

The range wouldn't likely be noticable imo,my guess is that the rc is out a fair bit with the lowered suspension combined with the relocated crossmember.I was able to move my inner end up 1.5" combined with a 40mm roll center adjuster(spacer between the arm and spindle)which puts it back close to stock.

It doesn't take much vertical change at the ball joint to affect the roll centre height significantly. Factors that will affect how much it moves will be the track, front view swing arm length, and length of lca. It looks like that example could move the bj over a 1" range but you should know where the nominal value is relative to stock to know how much it can compensate.

With most double wishbone suspension, the roll centre is generally designed to change height on a 1:1 ratio with chassis height. But on a mac strut car, as you lower the vehicle, the rc lowers alot more. That increased distance between the CG and RC means that you need to counteract that roll moment with a stiffer bar and or springs. Might sound counterintuitive to think that stiffer rates at the front will give you more traction but it ain't. It's about camber control, and the more the car rolls the less desireable the camber gets. If this is the case, then tire temps will show the outside hot on the laden tire even with a significant amount of static camber like 4.5deg.

[ADAM]

so over the weekend I built up a front splitter and one spare splitter as well...

built a mounting frame out of 1x1 tube steel..and the splitter out of plywood..it has a 4 inch extension..

plus lexan'd over all the holes in the nose instead of using duct tape...


so next event will be able to see if a splitter helps or not

[Sundown]

This may sound unrelated, but what type of differential do you run? Rear-drive Nissans have traditionally been very handling sensitive to diff changes.

Considering your big American mill is probably making a measurable amount of torque over the Nippon 4cyl. and earlier in the rev range as well this could be a major contributor to your big 'ole pushing problem.

If you're using a viscous type diff, the car will have a tendancy to push when you increase the pound feet of twist you put through the drivetrain.

Helical types are a bit of a mixed bag, mostly manufacturer dependent on how aggressive the lock is. I personally have no experience with helicals outside of front drivers.

A clutch type mechanical diff is your best bet for rotation, but it, like sorting out your suspension geometry, will require a lot of testing before it will be dialed in where you want it. The problem is having to tear down the diff every time you want to change how much locking the diff will provide.


Best of luck.

[philip_240sx]

IIRC Adam is running a Kaaz 1.5 way clutch style diff.

http://www.casc.on.ca/forums/showthread.php?t=14022

[ADAM]

yeah the stock unit was a VLSD i swappe dit out this year for a Kazz 1.5 clutch pack type...

either way the car was pushing....at least now the rear hooks up better

[a_ahmed]

Sorry to dig this thread up from the dead. I don't know if you're the only 240 guy on here or not, but I have a 240 I began to build and have a few state-side facts I have noted from guys who road race 240s.

I have yet to take her out to the track but I'm really looking forward to it... I prefer to just drive than spend time tuning, but it'll all be good fun and effort ultimately :)

From a few things I've gathered from guys state-side they point to a few weak points in the car's suspension, front geometry with the mcpherson suspension needing alot of camber (good), a lil toe out, rear needing quite a bit of toe in, very little camber, if in anyway dialing in more squat/dialing out anti-squat by tilting the subframe (bad anyways right lol) as the s13 chassis has tons of anti-squat dialied in by default (hence ideal for drifiting and going wee waa way sliding). S15 subframe apparently is the holy grail but ... meh... ultimately a completely redesigned subframe would rock (theres tons of talk of that on www.nissanroadracing.com (http://www.nissanroadracing.com))

I've got all SPL arms minus the FLCAs and RLCAs as they cost an arm and a leg...

From what I've gathered from what they've said ideal settings are usually like so:

Dropping car 2.0" without messing geometry too much...

Front
------
Camber: -3.0 to -4.0
Caster: 7.0-ish, i think stock is 5.5 or 6.5 or something? Higher does feel 'great' on street, but just too much steering effort, have yet to play with.
Toe:
0 to slight 1/16" toe out

Rear
-----
Camber: -1.0 to -2.0
Toe: 1/16"to 1/8" toe in
Shortening traction arm: 3/8" I shortened mine that much and they seem to like to shorten them more... apparently helps with bite in, it causes toe in under compression.

Also running no rear swaybar or the non-se non-hicas 15mm oem rear swaybar seems to be the thing to do.

For correcting roll center, honestly I dunno, SPL has those arms not sure how it's done or what, but on www.nissanroadracing.com (http://www.nissanroadracing.com) (should join), they have a whole thread discussing how to 'properly' correct the roll center and what have you... they still don't have a real solution other than many criticisism on possible solutions and lots of discussion...

My newb ass has a project thread on there but I'm just a newb. I hope to get more involved this year...I have an s13 hatch with 255/40/17 all around with koni 8611s and GC sleeves. 10.7kg/mm front 6" springs, 8kg/mm 7" rear springs. I need tender springs and spacers to lower the car... Initially as things stand I set it to -3.0 front camber, 0 front toe, 7.0 caster. Rear I shortened traction arm 3/8", -1.5 camber, and 0.12 (not inch?) toe in per side (the machine confused me and the whole inch and mm talks.. like I said im newb). Tanabe front swaybar with custom heim jointed endlinks and no rear swaybar. Solid subframe bushings.

The car is not bad, I have to yet get used to it but it does haul ass, I didn't add any compression left it as is for now... just added a bit of rebound front and rear... really have lots of work to do to it still tuning wise... have to take it out to the track. Just thought I'd share a bit of juice relating to s-chassis cars... come to www.nissanroadracing.com (http://www.nissanroadracing.com)

SPL parts are definetely quality parts. Their TC rods and tie rods are the best on the market period.

Also tire-wise for stock KA 245/40/17 all around or 255/40/17 all around is perfect. For higher power, 275/40/17 all around, one guy with front splitter and big ass wing ran 275/40/17 front and 295/40/17 rear relatively well... Some guys on 18s they run 285/30/18 front and 315/30/18 rear. Car doesn't like to be staggered too much, so keep all these things in mind. I'm mostly talking here based on other's experiences on s chassis, I'm just a friendly enthused newb :)

[ADAM]

thanks for the input...


however I solved 90% of the issues with the addition of a front splitter

[a_ahmed]

That's cool, I'll be a while before I do such a thing but it's on my wishlist :) I want to take advantage as much as possible of attaining as much mechanical grip prior to going to any aero on my project...

Do you have a thread where you show how you built it? I know you sent me a pic but it wasnt the underbody pics.

[ADAM]

its just plywood, and the supports are 1x1 steel tubing that is welded to the frame