View Full Version : 15's vs 16's, opinions wanted from people who have run both on an AW11...
ive raised the subject on here before, maybe more than once lol, but its still something that i cant make my mind up on
im firmly in the "small wheels" camp, id rather be running on 13x8" rims, but brakes tend to dictate things. i either want to run 15x7" or 16x7.5", but i am once again stumped as to which way to go, and need to decide soon as i need new tyres, and dont want to buy any until i have new wheels!
in terms of size, theres not much in it. with the 16's on 205/45/16 tyres id have about a 2.6% larger rolling radius over my current 195/50/15 (which are almost the same as standard), but 6% over the 195/45/15 profile id actually run on 15's if i were to stay on 15's (my current wheels are really nice, but dont accomodate my brakes! so i need new ones). sidewall height would actually be larger on the 16's so they wouldnt be excessively stiff, the slight ride height increase isnt an issue as i will have height adjustable struts soon. offset could still remain fairly close to standard, especially since the springs on my struts will be 2.25" and the spring platforms will thus be the same size, meaning loads of extra space in the inner arches. im also going wider on the arches once my fibreglass arches arrive so outside clearance is absolutely not an issue either
the only thing that is hindering my decision is handling/stability, and the extra weight.
the weight isnt so much of an issue, il be going with lightweight rims anyway, so the weight will still be a decrease over standard. 15" rims with tyres will weigh about 12-13kg each, 16" rims with tyres will weight 15-16kg each, standard rims are 16kg+ with tyres. obviously there is the matter of rotational weight, given that 16's will increase the mean radius, but again, i dont see this as a massive increase, not one that i think will affect things too drastically. and im making savings in unsprung weight elsewhere that will more than counteract the added weight of 16's
the stability of the car is something that does concern me though. im not sure that stability is really the right word to use, but im basically relating to the handling of the car with larger wheels, most notably tram lining. if im running 16's they will be running wider tyres, wider tyres have a tendancy to pick up the contours on the road a lot more readily, and the MR2's arent particularly planted at the front end to begin with!
so i just want opinions on how 16" wheels are to drive on the AW11, ideally from people who have also sampled 15" rims to get a direct comparison. i cant envisage the difference being massive, although im sure it will be noticeable. but the fact i can comfortably accomodate my ST185 brakes (my choice on 15" rims is being heavily limited by this!), maybe even upgrade to ST205 in future, run wider rims (as 16's are available in 7.5" width a LOT more commonly than 15's), wider tyres, and have more options available to me, are all persuading me towards 16's
the downsides are the increase in weight, increase in rotational mass, effects on handling such as tramlining, slightly more expensive, and tyres cost 30-50% more. on SOME rims they can look out of place on the MR2, but most of the ones im looking at would still suit the cars look, ive actually seen some 17's that look perfectly suited, i think the darker cars (like mine) can pull of bigger wheels than red and white cars, so thats not an issue
so, opinions please :)
I could be just spouting out random ideas but what would 15 at the fronts and 16 at the backs be like?
Would it reduce tramlining you are worryed about but still have the rear end grip that you want?
its the front brakes that im struggling to accomodate though :D. and id rather keep things balanced front to rear. the rear end grip isnt really an issue either, im running an open diff so im at the mercy of that in terms of traction, and id rather have more grip on the front. i prefer slight oversteer to understeer in my driving style
I've never run 15's on my current car but ive just swapped some 17x7 wolfrace wheels for my 16x7 OZ superleggera's. I have to say the difference is staggering, i wish i'd done it a year ago!
The car feels much more lively, its much more chuckable and its actually fun to drive now!
No more tramlining or rubbing on full lock or near the end of the suspension travel!
Ive got 195/45-16 on the front and 205/45-16 on the back.
I'm just about to make the swap up to 16's from 15's myself.
We had 14's on the coupé before and it was scary, got the 16" 'Azevs' on and the difference in grip and road holding was immense. Could still slide the car controlably out at the back end but the planted feel is so much better.
I like my 15's because they do keep that Elan school of handling opposed to outright grip feel, but on the V6 for sure i want the 16's.
There's nothing lost from going to 16's other than that seat of your pants, twitch which makes the trip to the shops fun. :D
sounds like 16's work pretty well then. it definitely gives me a lot more choice for wheels as finding used 15x7's is quite tricky, most people buy 6.5's. but finding used 16x7.5's seems to be a lot easier :)
let me know your thoughts once youve got some 16's on in place of your 15's Olber
keri-WMS
27-08-2007, 19:06
I'm running 215/40/16 Maragoni's on my 4-off rear Mk3 alloys - 16 (x7 from memory?)
I had 15's before that, and there wasn't a huge difference. A bit more grip and stability with the 16's (lower profile tires), a bit more chuckability with the 15's. As there's not exactly "tons" of front grip in the AW11 I prefer the 16's!
As for brakes, the 277mm WMS kit (and other calipers I expect) fit under normal 15's, with performance 15's you might just get to 300/310mm. For 16's add 25mm to this guide you should be able to fit 300mm or maybe 330mm at a push....
Marangoni's are awesome tyres, are they Zeta Linea's? softest tyres ever, they only last about 5000 miles, but they cost loads less than other tyres, and are awesomely fun :D
keri-WMS
27-08-2007, 20:39
Marangoni's are awesome tyres, are they Zeta Linea's? softest tyres ever, they only last about 5000 miles, but they cost loads less than other tyres, and are awesomely fun :D
They are indeed Zeta Linea's, and I agree about soft / fun but havn't had them too long! I always go for "cheap, soft, chunky" over "expensive, no grip, last ages, big name". :driving:
Marangoni's are awesome tyres, are they Zeta Linea's? softest tyres ever, they only last about 5000 miles, but they cost loads less than other tyres, and are awesomely fun :D
Really? I looked at these before, and thought 'cheap but crap budget tyre with designer tread pattern'? Then I noticed that the next door neighbour has them on his Evo 8....., so cant be that bad...?
yeh Marangoni's are totally unknown, but the rubber compound is ridiculously soft. you could never use them on a track because youd shred them in a couple of laps, but on the road they are fantastic
im getting a set for my new wheels, the boss had them on his old Corolla and reckons theyre the most fun this side of proper racing wets (which he also had on his Corolla on the road, Michelins no less :D)
Trying to get an understanding here of wheel sizes and why they effect the handling of the car. What is it that does this?
lower profile tyre.
Wider tyre.
?
I need a starting point to finding this out because I can sit and stare at google for ages but I just don't know what to type in for it to give me an answer.
Suitable offset for 16" wheels?
Depends on the width but i'd stick to the 35/40.
theres loads of ways a wheel will affect handling, unsprung weight, scrub radius, rolling radius, rotational mass/intertia, contact patch size, obviously it also determines tyre sizes, etc. and then because it determines available tyre sizes, youve also got to consider all the handling effects of tyres as well lol, of which there are even more!!
il reply a bit better this evening when ive got time :)
Trying to get an understanding here of wheel sizes and why they effect the handling of the car. What is it that does this?
lower profile tyre.
Wider tyre.
?
I need a starting point to finding this out because I can sit and stare at google for ages but I just don't know what to type in for it to give me an answer.
hard to find a logical place to start, so il just write it in whatever order it pops into my head. starting with wheel diameter, obviously the larger you go with the wheel, the heavier it will be. a heavier wheel means more unsprung weight (weight which doesnt act upon the springs. this mass has to be accelerated in order to move the suspension, so keeping it as low as possible is crucial for responsive suspension), which is obviously a bad thing. a larger diameter wheel also tends to dictate tyre profile as you dont want the rolling radius to be excessive, and lower profile tyres tend to have added sidewall stiffness. added stiffness in the sidewalls of the tyres can dramatically change the handling characteristics of the car, they tend to have more lateral grip overall, but break away more suddenly, the tyres take up less "slack" which puts more emphasis on the suspension (which can be a good OR a bad thing), they can create more work for the tyre tread, which can lead to increased wear rates, etc. then theres obviously the increase in rotational mass which means more intertia, e.g. the wheel is more willing to keep on spinning when you want to slow it down, and takes longer to get up to speed in the first place. a positive for larger diameter wheels though is that they create a larger longitudinal footprint which can aid with traction in a straight line, e.g. acceleration and braking.
wheel width is fairly important, generally going wider is better, up to a point. when tyres are mounted, they are ideally ever so slightly stretched on the rim, such that the sidewalls angle slightly inwards, as opposed to looking like a mushroom on the rim. this stops the tyres from folding under when under larger lateral loadings. also wider wheels mean wider tyres can be fitted, which means a wider footprint from the tread which leads to more grip. it also means less of the footprint is lost under the roll and camber change of the vehicle in cornering. but again, wider wheels are heavier, also there will more likely be clearance issues which can lead to people going lower on offset to space the wheels out further.
offset is best kept close to the manufacturer standard unless you know what you are doing by shifting it around. there is a characteristic of suspension geometry called "scrub radius", which is the distance between the centre of the steering pivot through the floor and the centre of the tyre tread. the larger the distance, the harder it is to turn the steering wheel, and also the harder the road will try to rip the steering wheel out of your hands. keeping the scrub radius to the minimum isnt necessarily the ideal, but you certainly dont want it to get excessively large or the car becomes physically straining to drive, and in a race car especially this is undesirable over longer distance races, when arms can become tired.
those are the things that have popped straight to mind, generally its better to run as small a wheel as you possibly can whilst still accomodating the braking requirements of the car. but if width can be increased on a small diameter wheel then that is worthwhile for accomodating wider tyres and keeping more rubber on the road in the corners. offset should be kept as close to standard as possible unless the benefits of accomodating a wider wheel (and using offset to overcome clearance issues) outweigh the drawbacks of increased scrub radius
This site has very good explanations of most things to do with tyres and wheels CLICKY (http://www.carbibles.com/tyre_bible.html)
So more offset will increase the scrub radius?
What about negative offset?
lodgeman
07-09-2007, 07:40
This site has very good explanations of most things to do with tyres and wheels CLICKY (http://www.carbibles.com/tyre_bible.html)
thanks jimi :thumbsup: will put a sticky on this info for further reference
It's a good site, if you scroll about halfway down the article it has a good calculator for working out the differences in RR for different tyre / wheel combinations, there's also one for working out the max wheel width a tyre will fit.
The whole site is very useful, it has sections on Brakes, Suspension and Oil / Additives.
I've had it bookmarked for a couple of years and it gets regularly updated and added to. :thumbsup:
So more offset will increase the scrub radius?
What about negative offset?
road cars almost always have positive offset as standard. the MR2 is about +39
if you go more positive then the wheel moves further inside the arch, and youll reduce the scrub radius (if one exists) upto the point that you zero it, after which youll increase it in the opposite direction, unless it started at zero in the first place.
if you go more negative on offset then youll move the scrub radius in the other direction and almost certainly increase it. people running actual negative offset wheels (e.g super deep dish) will find the steering incredibly hard to turn. my parts car came with ET25 wheels on it (only 14mm difference from standard) and you could really notice it on that, it was still driveable though, but i wouldnt want to go less than ET30 i dont think on an MR2. not because you couldnt physically turn the wheel, it still moves easily enough, but the feel of the car and the handling just isnt nice
:hijack:
what you are saying is that the wheel is tring to turn on a point that in not the center of the tire. like it would if you sat the tire on the ground not attached to the car and gave it a spin.
Can we measure this scrub radius easily or do we know it?
Would be interesting to see the scrub radius for mk1 and mk2, seeing as most people argue the mk2 is not as sharp as the mk1.
Can you adjust the scrub radius?
you can measure the scrub radius if you accurately measure an upper and lower point of the steering axis such that you can accurately plot the axis on paper/computer, and then you just have to measure the wheel centre relative to the steering axis so that you can also plot that
you cant really adjust it on the car (you can change camber which would also have an effect, but the camber change would have more significance than the scrub radius), the only way to really adjust it is to change the offset of the wheel. either with different wheels or with spacer plates.
So whats the best Offset for an Mk1 then?:)
standard, because its the only one that you can guarantee will work well with the car. anything else is subject to trial and error to find a "better" setup
Yeah but standard is with 14" wheels which i assume had narrower tyres on.
Offset is inner face distance from the centre of the wheel, isn't it? So on the 15's or 16's (with wider tyres) you want the same offset to "balance" the car on the centre of the tyres?
The width doesn't come into it.
Did i just prove myself wrong there? lol
I dont know olber but you've confused the hell out of me:slap:
Yeah but standard is with 14" wheels which i assume had narrower tyres on.
Offset is inner face distance from the centre of the wheel, isn't it? So on the 15's or 16's (with wider tyres) you want the same offset to "balance" the car on the centre of the tyres?
The width doesn't come into it.
Did i just prove myself wrong there? lol
offset is position of the mounting face relative to the centre of the wheel (which is the same as the centre of the tyre)
so whether you have a 5" wide wheel or a 10" wide wheel, the offset still puts the mounting face in the same place relative to centre. the difference is that a 5" wide rim with an ET25 offset would give the wheel a "dish" of 1.5" from the outer edge of the rim to the mounting face. whereas a 10" wide rim with ET25 offset would create a 4" dish
so a wider rim with the same offset would have more of a dish to it, but the scrub radius would remain exactly the same. the inner and outer edges of the wheel both move outwards by an equal amount, and thus wheel centre position doesnt change
So what about these people that go for the wide body kit for the Mk2. I would assume that TRD had their shit together when they picked the wheels for that. Maybe they came closer to the scrub radius than the standard mk2. And since a lot of stuff is shared between the mk1 and mk2 maybe that could be relevant to you guys aswell.
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