Fitting incorrect sized tyres

[Jez]

What would be the effect of fitting 275/30/19 or indeed 275/40/19 tyres to drive wheels which normally take 275/35/19?

Will either of those sizes be ok? Or should i stick to the original size?

 

[iaind]

From what i've read a maximum difference to the diameter of 2~3% is reccomended, both those sizes would change the diameter by 4%...

I'd stick to the original tbh, what would be the reason for the change in size?

 

[Jez]

The tyres i would like to buy are only manufactured in the sizes which i have posted I'll stick with the previous brand i used then.

 

[peterattheboro]

You're just changing the thickness of the tyre by a small amount so it should be ok?

The guy with the 'Stang fitted a tad larger tyre and it's fine.

Obviously check that a bigger size tyre wont be making contact inside the wheel arch.

 

[Ricochet J]

Is it for the Merc?

 

[Jez]

Yeah, for the S-class. They wont rub, but i am concerned about the speedo being wrong etc. Not sure it is worth it if it really will be as much as 4% as mentioned above.

 

[( |-| |2 ][ $]

If you went for the slightly taller tyre the speedo would under read.. (i think) so is it 100% accurate at the moment? If it over reads slightly you might end up with an accurate one?

 

[Jez]

Good point, i will have to check it and do the maths

 

[Kitchster_uk]

30's would be 4.2% slow, the 40's 3.9% fast. The fact they are 19's really does start to make a big difference.

 

[Jez]

Hmm, the 40's would put my speedo pretty much bang on, and i could get the tyres i want.

:/

 

[ganesh]

Go for the 40 then.

 

[BigglesPiP]

If you die can I have your rig?

TBH it will be fine. Maybe look at the final diameters of the tyres you can buy it on, see how much Merc were happy to vary.

 

[Django x2]

Jez, I roll on 275/30 R19 at the rear and just replaced mine. What were you looking to swap them with?

If anything, I'd go lower profile to avoid any arch catching, etc.

 

[Jez]

I want to get P-Zero, currently running RE050A If there is any issue with scraping i can raise the rear shock height slightly, but i dont think there should be. Still not sure though.

 

[saitrix]

Go for 40's, sounds perfect.

 

[neil-ste]

Changing the rolling radius of just the rear tyres may also have an effect on your ABS and or traction control, it'll think the rears are spinning at a different speed to the fronts

 

[[TW]Fox]

Why would anyone want PZero's so badly that they'd fit the wrong size tyres to get them? It's not as if they are particularly excellent or particularly good value?

 

[Jez]

They offer the lowest road noise and best ride quality of any tyres, at least according to many people running my same configuration over in America.

If there are quieter ones available, i am happy to be corrected and will consider any tyres

 

[Dangerous Dave]

There was a tyre review posted on here a few days ago where the PZero's won by a fair margin over the usual rivals including F1s and on checking they are give or take the same price. Hopefully another review will be carried out soon by Evo as the last one was almost 2 years ago and I am sure the designs/compounds etc may have been improved on in this time.

 

[Lum]

The smaller tyre will cause the speedo to overread, this is because the smaller diameter means the car covers less distance for each rotation of the wheel, and your car will be basing it's speed calculations based on how many times the wheel rotates.

Likewise, the larger tyre will cause the speedo to underread.

Since you are effectively changing the final drive ratio by doing this, the smaller tyre will also give you slightly better acceleration at the cost slightly lower top speed. Not sure if there will be a difference in fuel consumption.