Larger wheels adjustment

Anonymous · March 8, 2004, 09:20

OK, am I right in assuming that if you go from 16" to 17" wheels that your speed/mileometer needs to be adjusted accordingly.

Reason I ask is that in the new sillycar we covered 120 miles in 2 days, which is great, but we have sort of worked out that we dont think we actually did cover that amount.

I would "presume" that when Mr T put the 17" on the car they would have fiddled with the dials, but I have learnt not to assume anything with them. I need to call them to ask for my holding deposit back, will I look stupid asking the question about the miles?

markiii · March 8, 2004, 09:22

bigger wheels usually means lower profile tyres, which keeps the rolling radius the same.

so yes you would look silly.

Anonymous · March 8, 2004, 09:45

I'd be a bit stunned if they'd not sorted this... but you never know.

Tem · March 8, 2004, 10:18

m http://www.miata.net/garage/tirecalc.html m

Anonymous · March 8, 2004, 11:06

As Markiii said the tyre is usually lower profile consequently the rolling radius is the same ie no effect. Any changes will be marginal and if and dealer/garage said they had made any changes to the dials I would laugh in their faces s:wink: :wink: s:wink:

Only factor honestly worth considering when upgrading to larger wheels is the additional weight of the wheel(if applicable) and or the harder ride of lower profile tyres, other than that any changes to be quite honest are negligable and un-noticable

You often read wild negative statements regarding changing wheels to a larger size and decreased acceleration etc, these statements are usually made by the "leave your car looking like everybody elses" brigade and to be honest are more to justify their own course of action (or lack of it) s:wink: :wink: s:wink:

(stands back awaiting incoming fire )

Anonymous · March 8, 2004, 11:11

Cheers boys for the valuble advice as normal.

I wont say anything to Mr T then s:lol: :lol: s:lol:

I will however be installing the B2 at the weekend, and would obviously expect the usual 4mph outage in relation to the speedo...anything more than this would point to a problem...but I am now satisified based on your advise that all is well and happy.

You are of course all correct, the new 17's do in fact have lower profile tyres on than the stock 16's

SteveJ · March 8, 2004, 11:50

Quote from: "perry190"You often read wild negative statements regarding changing wheels to a larger size and decreased acceleration etc, these statements are usually made by the "leave your car looking like everybody elses" brigade and to be honest are more to justify their own course of action (or lack of it) s:wink: :wink: s:wink:

(stands back awaiting incoming fire )

OK - you wanted flaming so here you go

s:flame: :flame: s:flame: s:flame: :flame: s:flame: s:flame: :flame: s:flame: s:flame: :flame: s:flame: s:flame: :flame: s:flame: s:flame: :flame: s:flame: s:flame: :flame: s:flame: s:flame: :flame: s:flame: s:flame: :flame: s:flame: s:flame: :flame: s:flame: s:flame: :flame: s:flame:

A little applied maths ('A' level stuff) quickly shows why the acceleration is slower with the larger rims - even when the total weight is the same, the mass is further out on the larger rims, and hence requires more energy to get it moving.

Another (really nasty) side effect is the wheels act more like gyroscopes when you move the mass so far out, so when you try to change direction the wheel is fighting you by trying to stay in a straight line.

Impirical research with markiii's car shows that the 17" wheels and tyres (despite being only marginally heavier overall) robbed him of nearly .5 second to 60 (mind you that's not as bad as the 1.0 second he lost by using the decat pipe s:oops: :oops: s:oops: )

markiii · March 8, 2004, 11:53

not quite sure where the figures came from, but there definately was a difference.

However, that was with a couple of kilogram weight increase and a slightly larger rolling radius, both of which are bad.

While the theory regarding weigth placement is accurate, it also depends upon the weigth of your tyres, S)3 fr example are much heavier than Proxies.

Of course getting all the relevant weigths together and doing the math. is a little like hard work.

Now try and find a tyre manufacturer that lists the weigth of teh tyre.

Anonymous · March 8, 2004, 11:56

Quote from: "SteveJ"(mind you that's not as bad as the 1.0 second he lost by using the decat pipe s:oops: :oops: s:oops: )

I can just see mark sitting on a decat pipe trying to get to 60... still, a second slower than him in a car aint bad at all! s:wink: :wink: s:wink: s:lol: :lol: s:lol:

Anonymous · March 8, 2004, 12:19

Well we drive like girls anyway, and now we have a sillycar we will not be racing around as if we had a 2. YEAH RIGHT!.

Oh, I will not go into the fact that I raced a 03 roadster yesterday.

Anonymous · March 8, 2004, 12:26

s:lol: :lol: s:lol: s:lol: :lol: s:lol: s:lol: :lol: s:lol: s:lol: :lol: s:lol: s:lol: :lol: s:lol:

that woke you all up s:wink: :wink: s:wink:

Applied mathematics, cold fusion or quantum physics s:wink: :wink: s:wink: aside I have yet to notice any performance loss when upsizing from 15" to 17" or 16" to 18"

likewise all this talk of weigh reduction you hear in regards to batteries and exhausts etc? My 190 celica performed identically like for like against an identical car with a driver a good 3 stone heavier than me?

I'm sure these various theories are correct, however........ in the 'real world' where we are not competing in top level motorsport where every performance issue is measured at almost molecular/atomic level :-) :-) :-) then it makes sod all noticable difference unless the differences are major IMHO

If you bought a standard 190 celica whn it was new in 2001 it came with 16" wheels and tyres and had a quoted 0-60 by toyota

If however you bought it with a sports pack it came with 17" wheels and tyres yet toyota still quoted the same 0-60 time and top speed?

So do the 'toyota know best, so dont change it' gang dissagree with toyota on this one? s:roll: :roll: s:roll:

mph · March 8, 2004, 12:47

I definitely noticed a beneficial difference downsizing from 17s to 15, though I didn't notice the difference when I upsized.

Empirical evidence from comparing straight line acceleration on an airfield between my car (which then had the Unichip fitted, ~159bhp and 17" wheels) and pmdye's Roadster (stock with 15s) illustrated no comparable difference. Of course there could be 1001 other reasons why the extra power wasn't being demonstrated, however I put it down, rightly or wrongly, to the additional rotational inertia of my not-so-light 17s.

markiii · March 8, 2004, 12:50

Quote from: "perry190":lol: s:lol: :lol: s:lol: s:lol: :lol: s:lol: s:lol: :lol: s:lol: s:lol: :lol: s:lol:

that woke you all up s:wink: :wink: s:wink:

Applied mathematics, cold fusion or quantum physics s:wink: :wink: s:wink: aside I have yet to notice any performance loss when upsizing from 15" to 17" or 16" to 18"

likewise all this talk of weigh reduction you hear in regards to batteries and exhausts etc? My 190 celica performed identically like for like against an identical car with a driver a good 3 stone heavier than me?

I'm sure these various theories are correct, however........ in the 'real world' where we are not competing in top level motorsport where every performance issue is measured at almost molecular/atomic level :-) :-) :-) then it makes sod all noticable difference unless the differences are major IMHO

If you bought a standard 190 celica whn it was new in 2001 it came with 16" wheels and tyres and had a quoted 0-60 by toyota

If however you bought it with a sports pack it came with 17" wheels and tyres yet toyota still quoted the same 0-60 time and top speed?

So do the 'toyota know best, so dont change it' gang dissagree with toyota on this one? s:roll: :roll: s:roll:

I somehow doubt Toyota actually measured it with the options on.

Anonymous · March 8, 2004, 14:49

s:lol: :lol: s:lol: s:lol: :lol: s:lol: s:lol: :lol: s:lol:

If you mean

1.does it look like I give a f##k. Then I couldnt agree more s:wink: :wink: s:wink:

However if you mean

2.does it look like I've got any friends. I honestly wouldnt know Mark have you ? (apart from here) s:lol: :lol: s:lol: s:lol: :lol: s:lol:

markiii · March 8, 2004, 14:55

edited due to missing text.

Anonymous · March 8, 2004, 15:03

ah ha

surely not! s:shock: :shock: s:shock:

Mmmmm I wonder if TRD or TTE actually measure the performance of their mods or not Mmmmmm interesting.

How can life go on as we know it if the Roadster isnt perfect as it is after all s:shock: :shock: s:shock: , or 'god forbid' but do you guys think it could be at all possible that it can be improved on s:shock: :shock: s:shock: s:shock: :shock: s:shock: not possible surely! s:wink: :wink: s:wink: s:D

s:D

markiii · March 8, 2004, 15:20

I agree it can be improved.

but lets face it TRD quote 15bhp for a cacbox and inlet duct.

no way did they they get that figure by testing

I'm sure Toyota checked the times for the car as it was intended to be sold. Do I think they re-tested after some marketing/design bod decided on the bolt ons for the option pack? not really.

Anonymous · March 8, 2004, 15:22

Bluudy hell, and I thought I was going to look silly asking Mr T. Look at you all - GEEEEEEEEEKS! s:lol: :lol: s:lol: s:lol: :lol: s:lol: s:lol: :lol: s:lol:

Anonymous · March 8, 2004, 16:15

oh yes s:wink: :wink: s:wink:

Tem · March 8, 2004, 18:13

Quote from: "markiii"but lets face it TRD quote 15bhp for a cacbox and inlet duct.

Wasn't that for the duct, manifold and muffler...?

Anonymous · March 8, 2004, 21:49

Well Slacey is moving down from 17" to 15" - I wonder what his view is re. acceleration?

Or is he staying away to dodge the incoming fire (can't say I blame him really! s:D

s:D )

Sundance s8)

s8)

Slacey · March 8, 2004, 21:57

Quote from: "Sundance"Well Slacey is moving down from 17" to 15" - I wonder what his view is re. acceleration?

Or is he staying away to dodge the incoming fire (can't say I blame him really! s:D s:D )

Sundance s8) s8)

I dodge nothing! s:lol: :lol: s:lol:

I'll be honest, the car is sooo much nicer to drive on the 15's... the 'alertness' is back acceleration wise, the ride smoother, the turn in sharper and less understeery. I love the look of my 17's and will be keeping them, but for everyday thrashing, the stock wheels win it for me.

SteveJ · March 8, 2004, 22:05

Quote from: "Slacey"I'll be honest, the car is sooo much nicer to drive on the 15's... the 'alertness' is back acceleration wise

That'll be less rotational inertia then

Quote from: "Slacey"the ride smoother

That'll be less unsprung weight then

Quote from: "Slacey"the turn in sharper and less understeery.

That'll be less gyroscopic effect then.

s:twisted: :twisted: s:twisted: The prosecution rests s:twisted: :twisted: s:twisted:

markiii · March 8, 2004, 22:06

what size wheels are on the back of yours :-) :-) :-)

Anonymous · March 8, 2004, 22:10

16's by any chance? surely not s:lol: :lol: s:lol: