Tire width. How wide is wide enough?

[Jim Frahm]

MK4 Roadster


Okay, I know I’m going with 18” wheels and I know the max widths are 11” in the rear and 9” in the front. What I don’t know is, how wide should I go? I don’t plan on tracking the car but spirited driving is highly likely. My Porsche had 10s on the rear and 8.5s on the front and it handle like it was on rails.

I’d like to hear your experiences?

Thanks in advance!

Jim

[GoDadGo]

The wide tire folks tend to run the following:

......255/40-17 Front....315/35-17 Rear
.............................OR
......255/35-18 Front....315/30-18 Rear

..Some have even squeezed 275's up front.

[CraigS]

The wide tire folks tend to run the following:

......255/40-17 Front....315/35-17 Rear
.............................OR
......255/35-18 Front....315/30-18 Rear

..Some have even squeezed 275's up front.

The perfect answer.

[ggunter]

Could someone tell me where I can find a 315/30 or 35-18 preferably a Nito555 G2?

[JeffP]

Could someone tell me where I can find a 315/30 or 35-18 preferably a Nito555 G2?

They don't make the 555 in those sizes: https://www.nittotire.com/car-tires/nt555-g2-ultra-high-performance-tire/
315/40R18 is closest you'll get, and have fun finding them. Took me 4 mo to put together a set of Nt05's

[GoDadGo]

Could someone tell me where I can find a 315/30 or 35-18 preferably a Nito555 G2?

As you know Nitto doesn't make the 315/30-18 in the 555-G2, but here is a link that might help you find something subtable in that size.

https://www.discounttiredirect.com/fitmentresult/tires/size/315-30-18

Discount Tire sponsored Team Penski's Austin Cindric who just won the Daytona 500 yesterday.

https://www.discounttire.com/about-us/motorsports/nascar

[john42]

I have Toyo R888R 315s on the rear and I been chasing 255s for a while now. Long enough that I may squeeze 275s on the front instead.. Seems I can find 275s anywhere.... better then driving on rims or the dried out 10 year old Toyo RA1s.

note: 17in rims. So 315/35/17 and 255/40/17.. Or maybe 275/40/17 if this crazy back order doesn't let up. Probably just as fun finding 18s..

[Avalanche325]

I don't know what Porsche you have / had. But if it is older, it likely didn't have an issue with the power overwhelming the tires. If is is newer, it has traction and stability control and won't really let you overwhelm the tires unless you are REALLY trying.

On a Cobra with anything over about 350HP, I would go 255 front and 315 rear in a 200TW max.

[BEAR-AvHistory]

FWIW 275X40X17 fit stock FFR wheels & Mk-IV body without any mods with a 4" ground clearance. Sit inside the wheelwells. Rears are 315X35X17. Since there is no standard for tire measurements so you need to look at the mfg. spec numbers or Tire Rack numbers. My tires are NITTO NT01 whose physical measurements you can use for a base.

[bobm488]

I have 315X35X17 on the back of mine, sure seems like with the right rim you could go an inch wider.

[Jim Frahm]

I guess I need to clarify that I’m looking for the narrowest tires I can get away with, not the widest that will fit. However, Avalanche325 recommended to go wide if you have the HPs. My motor will be north of 450 HP so I guess I’ll go with the wide setup as recommended.

My kit arrives early next month. I have just about everything you need that’s not in the kit except wheels and tires. Time to go shopping.

Thanks for everyone’s input.

Jim

[AC Bill]

The make/type of tire itself has a major roll in it's traction abilities, not just, wider is better. You will find quality differences vary. I'd be looking more for advice on which tire to choose.

I'd bet not many fellows that built a roadster for street use, and having higher horsepower engines, rarely, if ever, test their tires ability's at the extreme end of the scale.

[rich grsc]

The make/type of tire itself has a major roll in it's traction abilities, not just, wider is better. You will find quality differences vary. I'd be looking more for advice on which tire to choose.

I'd bet not many fellows that built a roadster for street use, and having higher horsepower engines, rarely, if ever, test their tires ability's at the extreme end of the scale.
I agree, tire compound is more an important consideration for traction than just how wide the tire is.

[NAZ]

Compound is significantly important. Here's a good read but there is much more to the story. For those that don't like to read, the key takeaway is stickier tires increase traction not tire width. Tire width spreads the load over a larger area which is essentially making the tire stronger and better able to handle higher forces and increase wear resistance.

https://www.stevemunden.com/friction.html

(https://www.stevemunden.com/friction.html)

[Jim1855]

Just something to consider. Tires age out, nothing or little you can do about it.

While the current supply situation mandates early shopping and tires are important, they're also items that may not be needed until later in the build. For some this may be months for others much longer.

Watching the supplies and working appropriate timing would be wise.

I'm planning on 275/40-17 and 335/35-17, just hope they're still available when I need them. I'm a bit slow on the build.

Jim