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205 tires on 6.5 rim vs 245 tire on 8 inch rim


turbogrill
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Hi,

 

I know that tire widths is a hot topic that has been discussed many times. But I just can't decide.

 

For our next race we have two options:

205/50/16 on 6.5" rims

245/50/15 on 8" rims.

 

Car is a ~2600 lbs and has ~130hp.

 

Using the 205 tires  saves us a LOT of practical problems but how much better would the 245 tires be? 

 

Another option would be 225/50/16 on 6.5" rims, but it seems a bit narrow?

 

Thanks

 

 

 

 

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28 minutes ago, turbogrill said:

Hi,

 

I know that tire widths is a hot topic that has been discussed many times. But I just can't decide.

 

For our next race we have two options:

205/50/16 on 6.5" rims

245/50/15 on 8" rims.

 

Car is a ~2600 lbs and has ~130hp.

 

Using the 205 tires  saves us a LOT of practical problems but how much better would the 245 tires be? 

 

Another option would be 225/50/16 on 6.5" rims, but it seems a bit narrow?

 

Thanks

 

 

 

 

 

 

It's going to be tire specific.  Not all 205/50R16 are the same size.  Lean towards the 205, but knowing the specific tire helps.

 

Also, where are you finding 245/50R15? The only tire I know of in that size is a hoosier.

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2 minutes ago, Hi_Im_Will said:

 

 

It's going to be tire specific.  Not all 205/50R16 are the same size.  Lean towards the 205, but knowing the specific tire helps.

 

Also, where are you finding 245/50R15? The only tire I know of in that size is a hoosier.

 

Ooops! Typo!

 

These are my options:

 

- Dunlop Direzza Star Spec ZII  205/50/16 on 6.5" rim

- Dunlop Direzza Star Spec ZII  225/45/16 on 6.5" rim

- Dunlop Direzza Star Spec ZII  225/50/16 on 6.5" rim

- BFG Rival S 1.5 245/40/15 on 8" rim (heard bad stuff about these)

- BFG Rival S 225/40/15 on 8" rim

- Venturus 245/40/15 on 8" rim

 

I always struggle with tire width selection. 

 

 

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10 minutes ago, turbogrill said:

 

Ooops! Typo!

 

These are my options:

 

- Dunlop Direzza Star Spec ZII  205/50/16 on 6.5" rim

- Dunlop Direzza Star Spec ZII  225/45/16 on 6.5" rim

- Dunlop Direzza Star Spec ZII  225/50/16 on 6.5" rim

- BFG Rival S 1.5 245/40/15 on 8" rim (heard bad stuff about these)

- BFG Rival S 225/40/15 on 8" rim

- Venturus 245/40/15 on 8" rim

 

I always struggle with tire width selection. 

 

 

 

 

Rival S 1.5 came out in 245/40R15!!!!!  I thought that wasn't supposed to hit the market until June, need to get my hands on some of those.  

 

Your best all-rounder out of that set, and probably quickest for less-than-pro drivers is going to be the Rival S 225/40R15 on 15x8.  245 Ventus on an 8 will be pretty edgy and vauge - that tire is hard enough to drive on a 10" rim.  I'd expect the 245 Rival S to be grippier than the 245 Ventus, but no less difficult to drive. 

 

The Star Spec is usually wider than other tires of the same nominal width,  so those are going to be a bit iffy.  The 205 on 6.5" should be ok, but still a bit edgy due to the pinch.  I'd rank your options from best to worst:

 

Rival S 225/40R15 on 15x8

Direzza ZII 205/50R16 on 16x6.5

Rival S 245/40R15 on 15x8

Ventus RS4 245/40R15 on 15x8

Direzza ZII 225/45R16 on 16x6.5

Direzza ZII 225/50R16 on 16x6.5

 

Edit:  in general for racing:

8" rim for 205 section

9" rim for 225 section

10" rim for 245 section

 

Edited by Hi_Im_Will
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How much work is it to fit the 245s on the car?

 

But, it looks like the 15" wheels could be lighter than the 16s.  The tires should be about the same weight.   But the width is wider and the diameter is smaller to give you all that sweet get and go gearing.

 

Seems to me like the 225/40/15 on 8" is the way to go.

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The S in rival S stands for sux! At least for road course endurance...

 

However, you can get the good rivals (non s) from Jackson Motorsports Group and at good prices.

https://www.jacksonmotorsportsgroup.com/tire_sales/product/n47180

Call or email them for prices with shipping :) I think you will be surprised with their prices... Way better than tire rack and I don't think they carry the non s anymore.

 

Phone: 800-722-3234

Email: customer.service@jacksonmg.com

 

Edited by notbob
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1 hour ago, turbogrill said:

 

Ooops! Typo!

 

These are my options:

 

- Dunlop Direzza Star Spec ZII  205/50/16 on 6.5" rim

- Dunlop Direzza Star Spec ZII  225/45/16 on 6.5" rim

- Dunlop Direzza Star Spec ZII  225/50/16 on 6.5" rim

- BFG Rival S 1.5 245/40/15 on 8" rim (heard bad stuff about these)

- BFG Rival S 225/40/15 on 8" rim

- Venturus 245/40/15 on 8" rim

 

I always struggle with tire width selection. 

 

 

At least you have options.  For my Miata, 205s are it.  225s are too big without cutting stuff.  But we stretch those 205 over 7.5 rims.  

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4 hours ago, Kentite said:

We have had good results with 225/50R16 on 8" rims.

What kind of car is it?

It's a 280zx. 

4 hours ago, notbob said:

The S in rival S stands for sux! At least for road course endurance...

 

However, you can get the good rivals (non s) from Jackson Motorsports Group and at good prices.

https://www.jacksonmotorsportsgroup.com/tire_sales/product/n47180

Call or email them for prices with shipping :) I think you will be surprised with their prices... Way better than tire rack and I don't think they carry the non s anymore.

 

Phone: 800-722-3234

Email: customer.service@jacksonmg.com

 

 

Thanks! Will check it out. 

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I'd suspect you might loose some mph in each gear with the shorter wheel and might have to upshift on the track were you didnt have to before, but make up for it with better handling and better tire wear with the wider contact patch...225 on a 16x8 would be ideal

 

There is a reason Lemans prototypes are now running 20 and 21in wheels 

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Aerodynamic drag on a open wheel car with a dramatically taller wheel comes into play and better line of sight visibilty for an f1 driver an inch off the ground would be my guess to run a 13in wheel, but correct me if I'm wrong

 

you don't have to worry about aerodynamic drag with a fendered race car as much and your sitting significantly higher than an f1 car, so line of sight isn't an issue..

 

it also might be a safety issue with open cockpit/open wheel cars to have a substantially larger wheel

Edited by flboy7x
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F1 cars run 13" wheels due to regulations.  You know they would be running bigger if they could.   A larger wheel diameter with the same tire OD will be a heavier setup.  A taller tire will give you more top end speed but will affect your acceleration due to gearing. 

 

4 hours ago, flboy7x said:

There is a reason Lemans prototypes are now running 20 and 21in wheels 

 What is the reason?  Its not to clear big brakes.  LeMans is a unique circuit that sees very high sustained speed not found on most circuits.  I suspect it is about sidewall height and keeping the bearings and drive shaft speeds reasonable.

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