Going from 15 Halibrands to 17s....

[CliffBeer]

Wondering if anyone has any advice on going to 17 inch halibrands from 15 inch halibrands on a CAV?? Currently 215/60/15s on the front and 295/50/15s on the rear. I don't really want to go down to 40 and 30 series rubber on the front and rear respectively with the 17s. Thinking I could get away with 215/45s on the front and 295/40s on the rear. Hoping this doesn't shake my teeth out too bad.

I obviously know this will change the rpm of the motor per mph of velocity given the somewhat longer circumference of the rear tires. However, with the relatively high final drive of the audi transaxle in my CAV this might be a welcome change.

Any thoughts anyone?

ps. anyone know where to get 17 inch halibrands?

 

[JCoop]

Speak to Bob Lacey, He has BRM style 17" coming out soon; or maybe he has them already. They would retain the original look and be awesome on the CAV. He also has 17" Halibrand style in stock. Bob was the Western distributor for CAV so he knows the car well.
http://www.vintagewheelsus.com/

 

[CliffBeer]

Great, thanks. I'll give Bob a shout.

 

[JCoop]

Cliff,

I was thinking about this last night and thought 17" would alter too many things on the CAV. What's the reasoning,may I ask? Is it aesthetic, or handling/performance for tracking? Especially if you don't want to go to lower sidewall ratios. 1, it would raise the center of gravity of the car, 2, I think it would be too harsh a ride for the street. I think the correct replacements would be 315/35/17 and 275/40/17. I wish Steve R. from Cape Town SA would jump in here as I know he has 17s on his CAV.
Maybe check Roger Kraus' options on Avons or Goodyear blue streaks for performance.
I have 17s on my Cobra, and even with the taller sidewalls BFGs (40's instead of 35's in the rear, and 50s instead of 40s in front) the ride is way too harsh on the street for me. Love the look, though.

 

[CliffBeer]

JCoop, thanks, I think you're probably right - might be too harsh for street time and I plan on driving my CAV on the street a bunch.

The stock 15's come with 215/60 on the front and 295/50 on the rear. I'm thinking these are pretty high sidewalls, particularly the front, for really hard cornering on the occasional track day or run down a twisty road. I don't really want to get down to 35 and 40 series rubber as that's going to be pretty rough for commuting. Really just trying to find a reasonable compromise. Perhaps 16 inch Halibrands would be good - maybe go for some 235/50s front and 315/45s rear???

Your cobra looks great by the way!

Thanks.

 

[Bob Childress]

Hi Cliff,

Just like you said, low side wall will affect the harshness of the ride probably more than any other factor. However there is considerable variation between brands of tires. Try this link:

http://www.tirerack.com/tires/surveyresults/surveydisplay.jsp?type=MP

Ratings are included for harsh ride as well as road noise and performance.

Here are the tire and wheel specs for my mono CAV: Tires are Goodyear F1 GS-D3 Fronts - 245-40-YR-17 on 17 x 8 wheels Rear - 315-35-YR-17 on 17 x 11 wheels.

Suspension is set soft in the rear and harder in the front. I have had no tire or wheel problems both before and after my suspension modifications. Hope this is of some help. My car is also intended for mostly street use but I still went for 17 inch tires because of the YR ratings and the performance advantages. Any details or comparison measurements that you want I would be glad to share.

Bob

 

[Bill Musarra]

It might help if you give the spring rates of your cars, as that will effect the rideability of the cars on the street probably more than the aspect ratio. I too want to go to 17s, but my reasoning is the selection of rubber. There is much more selection for the 17s in every aspect. The lower ratios do have a stiffer sidewall, but the spring rates should offset them. I am looking for 315s or even 335s for the rear. Just have to make sure there are no fitment issues. The wheels will have to be carefully ordered to keep the tires where they should be.

Bill

 

[JCoop]

Bill, I agree too with the selection of tyres.
And, I'm almost sure the ride problem on my Cobra can be fixed with a change in spring rates. I currently have 475# 10" front and 475# 12" rear coilover springs. I and going to change to 400# front and progressive rate 175-375# for the rear. Somewhere here I recall reading the key to a nice street ride are softer springs and top notch shocks. I have QA1s 12 way adjustable so I think I have good shocks.

Bob, did you change the Spax coilovers on your CAV when you went with the 17's?