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Author: Subject: Bigger rear wheels to gear up
f27

posted on 8/9/15 at 08:16 PM Reply With Quote
Bigger rear wheels to gear up

Hi,

As a few of you will know I've been having problems with my diff ratio for my ZZR1400 Formula 27 (not enough top end). I have just purchased a 3.54 which should help, but I've also been mulling over increasing the rolling radius of the rear wheels to 'gear it up' more if needed.

I've currently got 15's on it with 888 tyres (I think they're 195-5015). I'd been planning to move to 13's to improve handling and reduce weight.

What would my options be? If I went to 13" could I get a tyre deep enough to increase the rolling radius? I would like to stick to 888's or AO48.

If it's not going to help, I guess I could either fit a deeper tyre to the 15's or even go bigger and get some 17-18's on the rear.

Has anyone else done this and what were your experiences?

Thanks in advance





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austin man

posted on 8/9/15 at 10:08 PM Reply With Quote
you could go for a 70 series escort in the say ran 175 70 13s should be able to get them in a 194 205 size





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CosKev3

posted on 9/9/15 at 05:57 AM Reply With Quote
Rear arch clearance will need checking,if the arches were mounted with a certain wheel/tyre size you might find a bigger radius will foul.
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Rosco86

posted on 9/9/15 at 07:16 AM Reply With Quote
have you used the gear ratio calculator to work out how much it will increase your top end before you go buying tyres?





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f27

posted on 9/9/15 at 07:34 AM Reply With Quote
Looks like 205-60-13 is the biggest diameter I could get in 13" R888s. Won't be much different to my current 15's, so I would have to look at 17-18" wheels.

There is plenty of room under the rear arches, so it should be ok if I do need to do it.

I used the gear calculator and it looks like it should be ok with the new diff, but in the real world the figures from the diff calculator are often wrong at the top end (from my experience). I haven't fitted the 3.54 diff yet, so the question about tyres is theoretical and just so I know I have another option if the new diff doesn't give enough top end.





- ZZR1400 Formula 27
- 750MC Locost racing car

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Nickp

posted on 9/9/15 at 02:47 PM Reply With Quote
You could go to 225/50/15 rears which will give you +5.2%, not massive but an increase none the less. These should give you the choice of track tyres from Toyo Yoko and Kumho.
There's also 205/60/15 and 225/60/15 listed on Camskill. These offer a 9% and 13% increase respectively but there'll but much less choice and you'll probably pay a premium for these odd bod sizes.
I wouldn't reccomend going to 17/18" as the only performance option come in very low profile (40/45) so you won't gain much (if any) at all and you'll pay a fortune for them.

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turbodisplay

posted on 9/9/15 at 03:25 PM Reply With Quote
Longer diff, I have ones that go to 2.47.

Bmw do 3.15 as well.

Darren

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f27

posted on 9/9/15 at 06:17 PM Reply With Quote
quote:
Originally posted by Nickp
You could go to 225/50/15 rears which will give you +5.2%, not massive but an increase none the less. These should give you the choice of track tyres from Toyo Yoko and Kumho.
There's also 205/60/15 and 225/60/15 listed on Camskill. These offer a 9% and 13% increase respectively but there'll but much less choice and you'll probably pay a premium for these odd bod sizes.
I wouldn't reccomend going to 17/18" as the only performance option come in very low profile (40/45) so you won't gain much (if any) at all and you'll pay a fortune for them.


Thanks for that, gives me more options to look at

quote:
Originally posted by turbodisplay
Longer diff, I have ones that go to 2.47.

Bmw do 3.15 as well.

Darren


For English axle?! The tallest ratio anyone had heard of was 3.54 and I spoke to a lot of diff specialists...

[Edited on 9/9/15 by f27]





- ZZR1400 Formula 27
- 750MC Locost racing car

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