BURL

Posting here caause I know a lot of you FI guys are drag racers. I'm doing a FI build that hopefully will be around 750 Flywheel HP in a car with all the standard bolt on's. It a 2003 that will have a LS2 forged lower transplanted. Running gas as fuel, a RPM A6 and 3.42 rear.

Now to the problem. I have polished thin spokes on stock stagger - 17" front, 18" rears. I want to keep these wheels. Yes I like them and will keep them. I want stealth for the street as well as the strip. The car will do occasional duty at the local 1/8 mile drag. I will be fitting drag radials to what ever rear rims I use. I will be keeping the 17" fronts but I have access to another set of 17" thin spoke fronts that could be widened for duty on the rear.

I think it about $250 per rim to widen. Is the 17" rims worth the cost in terms of traction and tire availability or should I just say good enough and run the origial 18's

Rkreigh

for all out the bigger sidewalls and taller tires can help with traction

that being said the MTs and other drag radials work well.

I went with both 17s and 16s and the 16s have more sidewall and hook much better

look more at the aspect ratio and see what sizes will fit

I'm running older RA1 335 18s and ran cup 18s 345 and when fresh they hook pretty good too but not enough for the digs

I like the MTs and the Hoosier DRs

BURL

Disregarding tire brands etc. in general if we get down to the heart of the question, do you feel the 17" rims will provide a pronounced advantage due to a little more sidewall.This won't be cheap to do - with shipping it'd gonna be about $300.00 per wheel to widen the 17"'s

Turpid porpoise

Would something like this work rather than sending your OE wheels out to be widened?

https://www.jegs.com/i/OE-Wheels/494/5910210/10002/-1

Podium

I wouldn't pay 500 to widen 17s for the rear. If your dead set on using the stock y2k wheels, I would try to fit the tallest tire you can on the 18.

BURL

This might be an option but it doesn't really match the shape of my factory polished spokes. The spoke is wider where it meets the rim but it's close. There was (I think) a factory version that match these and were wider at the meeting of the spoke and rim. Mine are the narrower version. Chrome won't match the polished surface either but in a pinch this might be the ticket with the Corvette center caps. Sometimes you got to compromise. It's certainly a cheaper way to go. Gonna keep it in mind as a option. Thanks

BURL

Turpid Porp. pointed out the C5 rims on Jegs. I had not seen them Looks like my decision is now to widen the 17" rins or just purchase two of these https://www.jegs.com/i/OE-Wheels/494/5910214/10002/-1 They are 10.5" wide 18's but that should allow a lot of tire width if they will fit OK under the car. I don't want tire sticking out past the body. These on have a +56 offset. Found this chart in the C4 section indicating a +58 offset for 10.5" wide 18" rim

Anyone know how these rims would fit ad if I will run into a "protrusion" problem?

neutron82

c4 zr1 wheels are 17x11 and will fit but the oems are harder to find, personally I wouldn't want replicas for anything other than driving on... you can use your 17x9.5 and use a 275 tire with a bigger sidewall, sidewall is more important than width

Turbo-Geist

A 17" tire and wheel combo is almost always going to provide better traction than an 18" tire and wheel combo especially if the 17" combo is taller or as tall as the 18" combo. There are some situations where people make 18s and even 19s work but it involves aftermarket ECUs and traction control.

What tire sizes are you planning to use?

You didn't mention your power adder of choice in this build but if it is a supercharger, the 18 inch combo may work ok with 750hp as torque will most likely be lower 6xx to the rw? One thing to be careful with is the torque converter. An aggressive stall to torque ratio on the converter will annihilate the tires and make the combo weak on the street without traction.

BURL

I may be misunderstanding your post but I'm keeping my polished thin spokes so that's the reason I'm considering widening 2 17"' OEM thin spokes for the rear - but only if 17's are a big advantage to the stock 18's. Alternately I might go to after market 17 X 9.5 or 18 X 10.5 rears if they are a close match to my polished wheels. Won't be doing C4 wheels. My current 17's are only 8.5" by the way. My original post may clear up what I'm trying to say.

neutron82

I understand you are keeping your 17s up front but if you had another set you could still run a good enough tire without having to widen them... but I thought they were 9.5" wide, 8.5" might be too narrow... oem c5z front wheels are 17x9.5 and will also work but if you are concerned about them matching then you would need a complete set... you can always run rear 18s up front with 17s in the rear... if you don't want it to disrupt the tc/ah then keep the rear tire at least 1/2" taller than the front but if you are only using them for racing then it doesn't matter since you will most likely have tc/ah off anyway

corvettebob1

You do know your Y2K thin spokes are prone to cracking where the spoke meets the barrel of the wheel, that's why GM went to the thicker spoke in later years.

BURL

.I going with Paxton SC.

I don't know about tires until I settle the rim thing but I realize tire availability for 17 vs 18 is part of the equation but I don't have the experience to pick tire sizes. When I settle on 17 vs 18 then I guess I'll move on to tire size

What you mention about torque converts is interesting also. I been reading for a year about people with 3600 ad 3800 torque converters and I'm thinking what's keeping these cars from going up in smoke on the line? If you do slicks you chance drive line failure and I just don't see how drag radials, especially with the deep low gear of the A4 can hold these 700, 800, 900 HP cars. In the back of my mind I've about settled on a 2800 stall. This is to be a street car occasionally raced. It's not a race car occasionally to be driven on the street.

I was hoping to find someone who has been through the 17 vs 18 rear rim issue to give some experienced advice. Now that I see how inexpensive some of these after market rims are the Jegs 17 X 9.5 and the 18 X 10.5 look interesting but as I said I don't know if the 10.5 will fit (with proper tire) under the car without sticking out on the sides. That 18 X 10.5 might be the way to go.

BURL

Everywhere I've looked lists the fronts as 17 X 8.5 and the rears as 18 X 9.5??

BURL

My car is an 03. Have always assumed they were the thinner spokes. Maybe not. What year was the change made?

ysb02

There will be a small difference between the 17 and 18 if you’re staying 26”. Probably not worth getting new rims though. I plan on running 17” 28” unless I find 15” cheap

BURL

Been a while sice you posted to my question. I've been doing more research on the 17" vs 18" rear rim question. I'm looking for max traction a the 1/8th mile with drag radials. You said in you post to fit the tallest tire possible. I can think of two reasons for this:

1. The 1st gear in the A4 is extremely low (too low) so the tall tire would slightly reduce the gear ratio in first.

2. The taller tire will have more sidewall ad more flex and provide better traction than a shorter stiffer sidewall.

Which is the reason you say get the tallest tire? Or is it a combination of both?

Thanks

fivelitrecobra

A taller tire will give you more sidewall. The larger sidewall will allow for more flex in the tire, which will be more effective at getting traction and transferring power to the ground. Watch a slo-mo launch of a top fuel dragster, same concept, just not nearly as extreme.


If I was in your shoes and looking for max traction, I would get the 17" wheels widened. You've already invested thousands of dollars into the build, what's a few hundred more. No point in cutting corners now. It gives you the wider wheels you want and keeps the look of the thin spokes that you are after. I would outfit them with some 28x11.50 MT Street R bias ply tires. Bias ply's aren't as street friendly as a radial, but you will get better traction from them.

BlackMagicC5

I have an 01 Z06TT and also want to keep the stock wheel look. Stock I have front 17x9.5 and rear 18x10.5. Im going to switch these and put the 18s on front and 17s on rear. I have a friend that did this and runs M&H 275/50/17 and it fits. Im going to try MT ET street R 305/45/17.

BURL

Sounds like a good plan. You will only be 1/2 under the suggested rim size for the 275/50/17's. However, my problem is the polished thin spokes I that I want to keep and currently have on my base model. They are 17 X 8.5 front and 18 X 9.5 rear. If I swapped front to rear I would be looking for a drag radial to mount on a 17 X 8.5" rim. Not very wide. Any ideas?