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17" Wheels Too Big?
mylesofsmyles - 24/3/07 at 05:00 AM

I want to throw a set of RS-Watanabe F817 wheels on my future Locost7 build. How big is too big and how wide can I go? I intend to run cycle fenders, 12" rears and and 8-9" front fenders.



I am thinking about a gray/gunmetal face with polish lip; my car will be lotus chrome orange!


[Edited on 24/3/07 by mylesofsmyles]

[Edited on 24/3/07 by mylesofsmyles]

zetec - 24/3/07 at 08:50 AM

If you are building a show car only and not too interested in the handling then you can fit what ever you like, it will fit one way or another. But if you are interested in getting it to drive as it should I would say that 15" with, max 7" width 195 or 205 tyres is as big as you want to go. Most cars of this type end up being less than 700KG so the size of the contact patch and the weight of the tyre need to be correct or the car will never handle as it should.

graememk - 24/3/07 at 10:12 AM

i have 16" 205s and to be honest there to big

when i change the tyres i'm going to go 15" 195's

Danozeman - 24/3/07 at 11:53 AM

I wouldnt go bigger than 15's unless i had a Big wide viento. I saw a westy at a show with 18's on. It looked ridiculous... The wheels were higher that the body. They were chrome aswell.

Angel Acevedo - 24/3/07 at 03:52 PM

There`s another thread where it`s discussed...
There are ride height and roll center issues if you change tire size.

Simon - 24/3/07 at 04:04 PM

I have 17's on mine and it's fine.

But, it is a slightly heavier locost

ATB

Simon

mylesofsmyles - 25/3/07 at 05:13 AM

I am clearly missing something here...how would having a larger wheel be a detrament to the vehicle's handling. Excuse my ignorance, I come from a household with much heavier, high-power, high-performance German and Italian cars; most of these come standard with 17", some with optional 18" and 19"...from my primative knowledge, larger diameter usually aids to the handling.

martyn_16v - 25/3/07 at 09:30 AM

New cars these days were designed from the start to have big bling wheels with little compliance in the tyres though, seven types generally aren't.

C10CoryM - 25/3/07 at 04:12 PM

larger wheels are not detrimental to handling...... in theory. In reality most wheels get much heavier as the rims get bigger. Especially OEM wheels as they need to be designed to handle more abuse. Bigger rims are needed because of bigger brakes. There is no other reason to upsize your rims. Unless the upsize makes for a lighter wheel of course.

RK - 25/3/07 at 05:41 PM

http://www.deman-motorsport.com/

These are 17" and they look hideous.

ChrisGamlin - 25/3/07 at 08:56 PM

Although any wheels will fundamentally work and if driven in isolation you would probably think they were OK, but there's several reasons why large wheels are a disadvantage on a light car.

As C10CoryM mentioned, when comparing a light weight 13" rim and a light weight 17" rim and you'll probably find the latter will weigh nearly double with no significant tyre weight advantage. Most 17" rim / tyre combinations weigh nearly 20kgs each, compared to maybe 12-13kgs for a 13" rim / tyre.

Larger wheels/tyre combinations also have more of their weight towards the very outer circumference, plus they weigh more to start with so there's far more gyroscopic effect. This means the wheels will be less inclined to change direction quickly, so adversely affecting handling particularly on a light car.

Another thing to take into consideration is that 17"/18"/19" tyres specifically designed for light cars is severely limited / non existant, the vast majority are designed for cars weighing maybe 1200-1600kgs, 2-3 times the kit car's weight. This means the compounds will never work as well as readily available 13/15" tyres (A048s / ACB10s etc) designed more for light cars, and the sidewalls will also be far too stiff.

cheers

Chris

mylesofsmyles - 26/3/07 at 12:54 AM

I think I like the look of the 17"

chockymonster - 26/3/07 at 08:07 AM

quote:
Originally posted by mylesofsmyles
I think I like the look of the 17"


If you like the look then go for 17s.
Get the car on a track and then swap for 13s and realise how much your bling wheels have altered the handling. On cars of this size and weight you really need the lightest wheels you can find/afford. I've learnt in the past how a poor choice of wheels that look good can destroy the handling of a car.

ChrisGamlin - 26/3/07 at 10:30 AM

quote:
Originally posted by mylesofsmyles
I think I like the look of the 17"


Yep, at the end of the day if thats more important for you than ultimate performance then they will still keep your brake discs from rubbing on the ground and you'll still think the car handles / accelerates very well, just be sure before you buy that you won't have that nagging feeling afterwards of what if.....

mylesofsmyles - 26/3/07 at 04:43 PM

I suppose you are all right; this just isn't the car for 17". I will opt for the 15"

PaulBuz - 26/3/07 at 05:58 PM

quote:
Originally posted by RK
http://www.deman-motorsport.com/

These are 17" and they look hideous.


You're kidding, right?!!
Amazing looking car!

RK - 26/3/07 at 08:52 PM

All in the eye of the beholder I guess. I prefer the retro look of the 13". Also, it seems most racing people use 13". Must be a reason for it and that would be weight I would guess.

blueshift - 26/3/07 at 10:03 PM

I was happy today to find out that my sierra alloys are 14", not 15" as I'd thought. I think I'll get them refurbed in black and use them for keeps on the locost.

I'm not into big wheels on locosts, 17" and above looks horrible I think, and with really thin rubber you get a very flimsy-looking wheel. just looks out of proportion and your brakes look really dinky unless you have some kind of monster overbraked setup, not to mention the weight and your screwed handling from the low profiles..

still some people think it's all about inches and the more the better

soggy 3 - 26/3/07 at 11:37 PM

It makes me laugh when people say ooh if you fit big wheels it wont go as fast as it will add an extra 20 kg, what the weight worriers forget is that even with 19 inch rims and a 1.3 crossflow these type of cars are quick and will always put a smile on your face,so go on fit your 17,s they look nice but not as nice as my 17,s

[Edited on 26/3/07 by soggy 3]

mylesofsmyles - 27/3/07 at 02:42 AM

quote:
Originally posted by soggy 3
It makes me laugh when people say ooh if you fit big wheels it wont go as fast as it will add an extra 20 kg, what the weight worriers forget is that even with 19 inch rims and a 1.3 crossflow these type of cars are quick and will always put a smile on your face,so go on fit your 17,s they look nice but not as nice as my 17,s


I intend to build this car for performance; I live in Northern California an d intend to take advantage of the great windy roads around here, there are no track events in the future of this Locost. I am of the rare few that favor the look of a bigger rim; not for the fact that it adds inches, I just find larger wheels, with low profile tires more appealing. My major concern wasn't in whether or not I could fit the 17" or if the ride will be compromised; the answers to this, I know. I am more concerned as to whether or not having bigger wheels with low profile tires will be a detrament to the handling of this little car. I am getting such mixed feedback, I think I will simply opt for my 17"...how bad can it be?

blueshift - 27/3/07 at 07:37 AM

myles, you seem to have quite selective reading or I've missed something.

All comments on the subject that I've ever heard are to the effect that small wheels are best for handling on a seven, not just because they are lighter but because of.. err.. things to do with sidewalls that other people can explain better than me

All racers and experienced car setup type folks I've ever heard comment on the subject agree.

The ONLY people I've ever heard promoting something as big as 17"s on a seven are people who like the way they look and say "I have them on my car and it handles fine".

I suggest to you that you may be happy enough with the way it drives on 17"s but if you are really into pushing the limits, if you switched to 13"s you would notice a great improvement.

NS Dev - 27/3/07 at 12:41 PM

quote:
Originally posted by blueshift
myles, you seem to have quite selective reading or I've missed something.

All comments on the subject that I've ever heard are to the effect that small wheels are best for handling on a seven, not just because they are lighter but because of.. err.. things to do with sidewalls that other people can explain better than me

All racers and experienced car setup type folks I've ever heard comment on the subject agree.

The ONLY people I've ever heard promoting something as big as 17"s on a seven are people who like the way they look and say "I have them on my car and it handles fine".

I suggest to you that you may be happy enough with the way it drives on 17"s but if you are really into pushing the limits, if you switched to 13"s you would notice a great improvement.


Hit the nail on the head perfectly.

What people are failing to realise is that the tyres on a light car actually carry out a great deal of the springing.

With the cheap (i.e. sub £250 apiece) dampers that we all use, their damping and springing in the very small movement range is extremely poor. Here the high profile tyres help, by acting as springs and dampers neatly combined in a rubber ring.

If you drove a car fitted with steel rings for tyres you would not be surprised if it wheelspun and handled badly.......................

Effectively this is what you are doing by fitting low profile stiff-sidewall tyres to a light Locost. Before you say that is rubbish, think about something like a tank or other extremely heavy vehicle. Fitting this with steel wheels would not be a big problem as the weight would distort both road surface and "tyre" in much the same way as a car distorts a rubber tyre. Remember that both the tyre and the road under it distort, they need to in order for any traction to be effected (and is why road surfaces break up over time)

Now go back to the locost, we need to fit high profile tyres to maintain tyre flexibility and thus correct contact patch and traction.

Next consider unsprung weight....................or more correctly, and never quoted by many other than me "SPRUNG TO UNSPRUNG WEIGHT RATIO"

Again make it simple to visualise, picture a 2 tonne wheel attached via a spring to a 1tonne car. You go over a pothole and what bounces? The car of course, not the wheel! Now bring it back to normal situation. A 25kg unsprung weight at one corner of a 1200kg family car is 48:1 ratio. The same assembly fitted to a 500kg locost is 20:1 ratio, making the wheel effectively 2.4 times harder to control over bumps.

Over unsprung kg saved makes the life of your cheapo Avo, Gaz etc dampers much easier, and you handling much better.

Hope this helps

Nat

ChrisGamlin - 27/3/07 at 05:50 PM

quote:
Originally posted by soggy 3
It makes me laugh when people say ooh if you fit big wheels it wont go as fast as it will add an extra 20 kg, what the weight worriers forget is that even with 19 inch rims and a 1.3 crossflow these type of cars are quick and will always put a smile on your face,so go on fit your 17,s they look nice but not as nice as my 17,s


Errm, us "weight worriers" aren't forgetting anything, nobody has said it wouldnt be quick and wouldnt handle OK with 17" wheels but it will be even quicker and handle even better if it weighs 20kgs less and has 13" wheels!