Help me chose a wheel/tire combo...

[GregR]

Morning! First-time user of the forum, and before the Solo-2 season starts in spring, I need to get new rims and tires (still using blech stock stuff). Car is a '99 Prelude SH, lowered 1.8" with H&R Race / KYB AGX.

Most 5th Gen Prelude people run 225/50-15's, but the new Kumho Ecsta V700's are also available in some good sizes, which gives me more options and thus more headaches! (Stock tires were 205/50-16, heavy as hell, 24.1" overall diam)

The sizes I am considering are:

225/50-15 (23 lbs tire, 23.7" diam)
225/45-15 (21 lbs tire, 22.8" diam)
205/45-16 (19 lbs tire, 23.0" diam)
205/40-17 (19 lbs tire, 23.3" diam)

Here's the deal - the 17's are up to 4 lbs lighter than the 15's, and I'm sure I can find reasonably priced 17" rims that are less than 4 lbs heavier than 15" rims to make up the difference. Seeing as the tire is the furthest thing out from the centre, my logic would say to go with the 16" or 17" and find the lightest rims for them.

Or is there some magic that happens with 15's that I haven't figured out yet?

[Chris P]

225/45-15 (21 lbs tire, 22.8" diam)


you want the smallest lightest widest rim possible. Also the 45 series tire will help with gearing.



I'm sure marsh will have something to say......

[Marsh]

Originally posted by Chris P
225/45-15 (21 lbs tire, 22.8" diam)


you want the smallest lightest widest rim possible. Also the 45 series tire will help with gearing.

I'm sure marsh will have something to say......

Yes I do. The 225/45-15 is the size of choice. The gearing is very noticeable. The only problem is it only comes in the v700 Ecsta, which I didn't like very much. Great straight line, but the side wall was way too soft for a 3000lb car like the Prelude. I'm going back to the V700 Victoracer in 225/50-15 this year

[Dave]

I miss my 5th gen Prelude! It never blew up on me!

The Kosei K1 rims are still a tough value to beat in a 15x7'' rim like you'll want for your Prelude. Fairly light at 13 lbs, strong as hell (I've beat on my for 3 years now and they've stood up to it very well), and look pretty good too.

The smallest diameter you can fit is a 15'' with the Lude rotor size, so go with 15's. Wider is better, so stay away from the all too common 15 x 6'' or 15 x 6.5'' rims and look for 15 x 7''. Team Dynamic Pro Racing 1 look promising (same weight as the Kosei K1).

If you've got a big turbo on your wallet, get some Hoosiers daddy! If your wallet is naturally aspirated, the Kuhmo V700 or the old Victoracers or Toyo RA-1's are all good values. I think the general consensus is that the Kumhos are stickier but the Toyos last longer and perform at their peak grip level for longer.

Happy shopping! Since you're in Ottawa, Talon Tire in Montreal isn't too bad of a drive and they're an awesome shop. Very well stocked, very competitive prices, very professional and knowledge staff.

Oh yeah, the magic is lightness. You can't get a 16'' or 17'' rim as light as a 15'', price being equal. Bigger is heavier and heavier hurts your acceleration considerably due to the effects of rotating mass and unsprung weight. These are evil things in motorsports terms.

[GregR]

Originally posted by Marsh
Yes I do. The 225/45-15 is the size of choice. The gearing is very noticeable. The only problem is it only comes in the v700 Ecsta, which I didn't like very much. Great straight line, but the side wall was way too soft for a 3000lb car like the Prelude. I'm going back to the V700 Victoracer in 225/50-15 this year

Hmm... I guess the smaller overall diameter and wider rim setup are the way to go... Thanks, guys - I'll stick with 15" rims, lightest from what I can afford...

Hey Marsh - what rim width were you running with the 225/45-15's..? I'm thinking of going 15x8 or maybe even 15x8.5 since the tech guy at Kumho I talked to just now recommended going as wide as possible (I can use 225/45-15 or 225/50-15's on an 8" wide rim, but only 225/45-15's on the 8.5"). I have a feeling most Preluders are using 15x7 - is there a clearance issue if I go any wider than 7"..?

I'm nuts enough not to worry too much about what class I end up in for Solo-2 (I'm doing this just for the fun of it and the experience), so rolling the fenders or even pushing them out (or even as far as making new ones out of carbon fiber) isn't out of the question...

What says youz?

[JGraves]

Greg, talk to Trent at tirerack trent@tirerack.com or 800-428-8355 ext. 268 about the 15x8 K1's. He frequently posts to the Miata forum and was very helpful when I bought the SSR's.

I forgot to mention it this morning but if you're comparing tire weights, you should at least look at the same width and overall diameter.

Jeff

[Marsh]

Originally posted by GregR

Hey Marsh - what rim width were you running with the 225/45-15's..? I'm thinking of going 15x8 or maybe even 15x8.5 since the tech guy at Kumho I talked to just now recommended going as wide as possible (I can use 225/45-15 or 225/50-15's on an 8" wide rim, but only 225/45-15's on the 8.5"). I have a feeling most Preluders are using 15x7 - is there a clearance issue if I go any wider than 7"..?

What says youz?

I'm running 15" x 7" I don't know if you can get a 15 x 8 to fit? 45mm offset is what I'm using for the 7". Bare on mind that there is a dimishing return with rim width, plus wider is heavier. I wouldn't bother with 8.5", but 7.5" would be a deffinite improvement. That size wasn't available when I ordered mine, that's why I have 7".

[GregR]

Originally posted by Marsh
I'm running 15" x 7" I don't know if you can get a 15 x 8 to fit? 45mm offset is what I'm using for the 7". Bare on mind that there is a dimishing return with rim width, plus wider is heavier. I wouldn't bother with 8.5", but 7.5" would be a deffinite improvement. That size wasn't available when I ordered mine, that's why I have 7".

Imagine the timing... I just talked to Trent at TireRack, and I could get a 15x8 in a number of offsets (12, 22, or 32)... Only thing I have to do now is start taking some measurements to see if I'll start scrubbing the inner bodywork with the wide rim/tire combo.

Oh, he also mentioned that the Ecsta V700's are stiffer than the VictoRacers but you have to run them shaved... I mentioned your experience with the 225/45-15's and he mentioned that teh tread blocks would sometimes squirm a bit - so maybe that's what you felt as a less-than-stiff sidewall...?

I'm gonna give the Ecsta ones a try, with hopefully a 15x8 rim (if that fails to fit, 15x7 is the way to go for me)... I can't afford to run Hoosiers on both street and track and replace after less than a month, but I CAN afford to get a second set of Ecstas half way through the season...

[JGraves]

I seem to recall hearing that K1's are available from tirerack without a bolt pattern, so all you have to worry about is offset. I know K1's are available in 15x8 and they use hub centering rings, I don't know what offsets are available or what no bolt pattern means (does tirerack drill or does the end user find a machine shop?). I would be surprised if there was more than 1.5 lbs difference between a 7" and 8" wide rim.

Jeff

[roooo]

Team Dynamic Pro Racing 1

Hmm.. I wish I could find a shop that has info about these wheels already! :confused:

[Marsh]

Originally posted by GregR
Imagine the timing... I just talked to Trent at TireRack, and I could get a 15x8 in a number of offsets (12, 22, or 32)... Only thing I have to do now is start taking some measurements to see if I'll start scrubbing the inner bodywork with the wide rim/tire combo.

Oh, he also mentioned that the Ecsta V700's are stiffer than the VictoRacers but you have to run them shaved... I mentioned your experience with the 225/45-15's and he mentioned that teh tread blocks would sometimes squirm a bit - so maybe that's what you felt as a less-than-stiff sidewall...?

I'm gonna give the Ecsta ones a try, with hopefully a 15x8 rim (if that fails to fit, 15x7 is the way to go for me)... I can't afford to run Hoosiers on both street and track and replace after less than a month, but I CAN afford to get a second set of Ecstas half way through the season...

-Non of those offsets will fit in a million years!

-Anyone that says the Ecsta is stiffer than the victoracer needs to have their house searched for a growing opperation! The Ecstas aren't much stiffer than my street tires! BTW the tread design of the Ecsta gives it a stiffer tread pattern. I think your contact might have the two tires confused.

I ran 38mm offset on a 7" rim and it stuck out past the fender. With less than 30 lb in the tires they were illegal under the Solo rule book (fortunately I ran more than that). Stock offset on the 5th Gen Prelude is 55mm.

[haniforama]

Originally posted by Marsh
-Non of those offsets will fit in a million years!

I ran 38mm offset on a 7" rim and it stuck out past the fender. With less than 30 lb in the tires they were illegal under the Solo rule book (fortunately I ran more than that). Stock offset on the 5th Gen Prelude is 55mm.

Marshall,

I have to disagree with you.

If you used a 45mm offset on a 15 X 7", you have plenty of clearance with the 5G Prelude. If you split the difference of the 1" wider wheel to keep the inner clearance the same, you decrease the offset by 13mm which would be 45mm-13mm=32mm.

I'd recommend the 32mm (one of the available choices) offset in the 15X8" and then roll the fender lip to gain the necessary outer clearance.

I love math!

The second thing i disagree with is to stick to a 7.5" wheel. The 8" or 8.5" will definitely perform better because it will allow the tire sidewalls to take a more vertical stance which will increase their ability to transfer the cornering loads to the wheel. I suspect you choice to run the 225-45-15" V700 on the 7" wide wheel is what is causing you to think that the sidewalls are "soft". I would wager (one dalla !!) that you could gain 1-2 seconds a lap running those tires on an 8" wide rim.

BTW: I'm hopefully going to have a set of 15X8" wide wheels on my Civic next year!

Hanif

[GregR]

The more I think about this and the trade-offs, the more I want to pull my hair out..! Running a 15x7 is a known fit, but a 15x8 with the right offset SHOULD be better given the same 225/50-15 tire. Actually, I found another quite light (and equally affordable) 15x8 rim that I can get in a 38mm offset (as well as 32mm).

Okay - so has anyone here tried or heard of experiences with Circle Racing wheels..? Those are the guys who can make a 15x8 in 38mm or 32mm offsets. Forged aluminum centre with a spun rim, for under $200 US each. When I called, they don't recommend them on the street, but I'm way too tempted to get those instead of the Kosei's and run them on both street and track. Might have to make some fender flares (or whole new fenders altogether).

Decisions decisions.......

[Marsh]

Originally posted by haniforama
Marshall,

I have to disagree with you.

If you used a 45mm offset on a 15 X 7", you have plenty of clearance with the 5G Prelude. If you split the difference of the 1" wider wheel to keep the inner clearance the same, you decrease the offset by 13mm which would be 45mm-13mm=32mm.

I'd recommend the 32mm (one of the available choices) offset in the 15X8" and then roll the fender lip to gain the necessary outer clearance.

I love math!

....

Hanif

Then maybe you should invest in a new calculator?

It's not 45mm - 13mm! That would move the wheel further out! The first time he crossed a pavement seem the fenders would slide through all four tires like cookie cutters.

It's 45mm + 13mm = 58mm! So a 60 offset should fit with an 8" rim

[haniforama]

Originally posted by Marsh
Then maybe you should invest in a new calculator?

It's not 45mm - 13mm! That would move the wheel further out! The first time he crossed a pavement seem the fenders would slide through all four tires like cookie cutters.

It's 45mm + 13mm = 58mm! So a 60 offset should fit with an 8" rim

Marsh - you're both right and wrong:

Your calculation is based on keeping the outer lip of the rim in the same spot - mine was based on keeping the inner lip the same, but your comment that the wheel would move further out is exactly right; that's the whole idea. If you didn't move the wheel outward, you'd cut the inside lip of the wheel on the front suspension pieces and also take out a nice chunk of the rear trailing arm. You MUST bring the wheel out the extra half of the wheel width to allow the inside lip of the wheel to land in the same spot. My secondary comment to roll the fender lip should prevent the cookie cutter fenders from damaging the tires on the ouside.

Hanif

[Marsh]

I thought that rolling the fender is an automatic bump to Street Prepared, but now that I check the rules it's allowed in SS. But you won't get enough clearance by just rolling on the back of the Prelude. You will need to cut the fender and that is a SP mod.

[JGraves]

Greg's Prelude is already a CSP car and he not overly concerned with what class he competes in. The car already has lowering springs (H&R race?) and KYB AGX shocks, very little interior and he is playing with making a few carbon fiber body panels.

BTW He work's with me in Ottawa and has done a few Solo 2's with MCO.

[GregR]

Yeah, H&R Race with KYB AGX and other silly mods. First carbon/kevlar panel will be the stinking heavy hood (hoping to go from stock 50-pounder to a 7-pound composite). Reading over the Solo-2 rules it seems like in CSP I am allowed to be sticking out past the fender edges, so I should be able to deal with a smaller offset (ie.: 15x8 ET 32mm) and not have to make composite fenders right now.

Option 2 is using 17x7.5 as street rims (cheap and reasonably light) with 205/40-17 Kumho Ecsta V700's for the first few events until I can swing really light proper 15x8's. I'm tempted to go with the 17x7.5 option right now because it's cheaper (I'm a poor sap right now) and I know I won't have fender clearance issues to deal with this early on in the game.

Oh - Jeff: I went to RMR Autosport in Montreal to check out a few Sparco seats - they have almost all of them and are only 1.5hrs away! Pretty good prices and they fit quite well, but I think I'll go with the Corsa since it looks to have the shoulder harness holes at the right height for me (the others are too low and result in evil close-to-45 angles).

[ice/solo racer]

I couldn't help noticing a possible error(I might be making one as well)Hanif stated his calculations were based on keeping the inside edge of the rim where it was and just adding a wider rim,but only added half of the extra rim width into his numbers.So instead of increasing offset by 13mm shouldn't he be adding 26mm to his 45mm starting point?
I'm no expert so if I've made an error forget what I say,but I just thought I'd add my observations.

[JGraves]

Offset is measured from the centerline of the wheel to the mounting surface. Backspacing is measured from inside edge of the rim to the mounting surface. Hanif is trying to keep backspacing the same to have the same clearance from the inside edge of the rim to the suspension components.

The centerline of the wheel is always in the center of the width, ie a 7" has 3.5" on either side of the centerline and a 8" wheel has 4" on either side of the centerline. Therefore to maintain the same backspacing you most subtract half of the width increase from the original offset.

For example you have 7" wheels with 50mm offset and want to change to 8" wheels

Backspacing of the 7" wheel is 7"/2+50mm=5.5"
Offset for 8" wheel is 5.5"-8"/2=1.5" or 38mm

Hope this clears up your confusion,
Jeff

[ice/solo racer]

Thanks Jeff,I guess thats why I just tell the tirerack what I'm driving and they send what fits!:D