Tyre profile VS sidewall stiffness?
Discussion
The local roads are very poorly paved, full of hideous potholes. They're a disgrace.
So naturally I want a quick car to drive on them. I could stick with 18" wheels and fit non-runflats but not all tyres are created equal. Some are very stiff regardless and some less-so. Is a stiffer, higher profile non-runflat 17" tyre a better choice for ride comfort over a softer, lower profile non-runflat 18"? Which would give better cornering (not the absolute highest priority but still very important).
The roads are really, really bad....
So naturally I want a quick car to drive on them. I could stick with 18" wheels and fit non-runflats but not all tyres are created equal. Some are very stiff regardless and some less-so. Is a stiffer, higher profile non-runflat 17" tyre a better choice for ride comfort over a softer, lower profile non-runflat 18"? Which would give better cornering (not the absolute highest priority but still very important).
The roads are really, really bad....
It's an E89, 35i so tipping the scales at around 1600kg. The smallest wheels are the seventeens, which mount 225/45 tyres front and 255/40 rear or 45 profile all around can be fitted perhaps, I'm told. An option on lower spec cars is 225 tyres all around, not the best idea with 300+ horsies. The car was optimised for Runflats but that'll be on German roads no doubt, not the Beirut we enjoy here.
I suppose the front tyre walls are stiffer but higher for the same amount of comfort as the softer, lower rears but improved steering response? Would that essentially mean getting XL tyres, which are stiffer, up front and normal rears? There's so much to consider; asymmetrical tread patterns can tramline badly on poor road surfaces, for instance i'm told, but as usual all tyres have confliciting reports and reviews. Michelin Pilot Super Sport? "Oh, these are noisy as hell" vs "These are very quiet!"... Vredestein Ultrac Sessanta? "Oh, you can mount kerbs with ease" vs "they offer NO rim protection!"...
It's because these reviews are from different cars of course, but it confuses the hell out of me...
I suppose the front tyre walls are stiffer but higher for the same amount of comfort as the softer, lower rears but improved steering response? Would that essentially mean getting XL tyres, which are stiffer, up front and normal rears? There's so much to consider; asymmetrical tread patterns can tramline badly on poor road surfaces, for instance i'm told, but as usual all tyres have confliciting reports and reviews. Michelin Pilot Super Sport? "Oh, these are noisy as hell" vs "These are very quiet!"... Vredestein Ultrac Sessanta? "Oh, you can mount kerbs with ease" vs "they offer NO rim protection!"...
It's because these reviews are from different cars of course, but it confuses the hell out of me...
Different tyres work differently in different sizes on different vehicles.
In short, your requirement of good steering feel / quick turning and good ride comfort are generally balanced against each other (not entirely true, but you know what I mean)
A softer sidewall tyre like the Uniroyal Rainsport 3 would offer more comfort in 18 inch than a hard sidewalled (non runflat) tyre in 17".
For optimum comfort something like the Rainsport 3 in 17 inches would give you excellent comfort and good cornering grip, but it would feel quite slow to steer on a big heavy car like yours.
In short, your requirement of good steering feel / quick turning and good ride comfort are generally balanced against each other (not entirely true, but you know what I mean)
A softer sidewall tyre like the Uniroyal Rainsport 3 would offer more comfort in 18 inch than a hard sidewalled (non runflat) tyre in 17".
For optimum comfort something like the Rainsport 3 in 17 inches would give you excellent comfort and good cornering grip, but it would feel quite slow to steer on a big heavy car like yours.
Visionist said:
An option on lower spec cars is 225 tyres all around, not the best idea with 300+ horsies.
Don't see why not. I have 300 horses going through 225/50 16 on my 944 Turbo, and it's absolutely fine. I would go on 225/45 17 all round on that if it were my car. Definitely non run flats. Edited by Lowtimer on Friday 31st October 12:59
Lowtimer said:
Visionist said:
An option on lower spec cars is 225 tyres all around, not the best idea with 300+ horsies.
Don't see why not. I have 300 horses going through 225/50 16 on my 944 Turbo, and it's absolutely fineIn general for comfort you want high sidewalls.
Other considerations are unsprung weight. 17s should be lighter than 18s so that would help too.
OEM wheels can be very heavy. If you can be bothered to do the research then there may be lighter OEM options or of course the aftermarket.
CrisW said:
Other considerations are unsprung weight. 17s should be lighter than 18s so that would help too.
OEM wheels can be very heavy. If you can be bothered to do the research then there may be lighter OEM options or of course the aftermarket.
Lighter wheels will make life much easier for the suspension over bumps.OEM wheels can be very heavy. If you can be bothered to do the research then there may be lighter OEM options or of course the aftermarket.
Non-run flat tyres are lighter than their runflat equivalents, sometime massively so. On my X5, up to 3kg per tyre.
Visionist said:
The smallest wheels are the seventeens, which mount 225/45 tyres front and 255/40 rear.
I’d do this.Visionist said:
I suppose the front tyre walls are stiffer but higher for the same amount of comfort as the softer, lower rears but improved steering response? Would that essentially mean getting XL tyres, which are stiffer, up front and normal rears?
Nonononononono, no. 225/45 and 255/40 will have sidewalls of exactly the same height. It is very important on a BMW that the tyre spec and construction is the same front and back, get your speed and load ratings from the handbook and if you’re going to fit XL tyres, get XL all ‘round. It is differences in tyre construction front to rear which can make BMWs feel pretty strange. Visionist said:
There's so much to consider; asymmetrical tread patterns can tramline badly on poor road surfaces, for instance i'm told, but as usual all tyres have confliciting reports and reviews. Michelin Pilot Super Sport? "Oh, these are noisy as hell" vs "These are very quiet!"... Vredestein Ultrac Sessanta? "Oh, you can mount kerbs with ease" vs "they offer NO rim protection!"...
Both of these are great tyres, as are the Goodyears, Continentals and Dunlops. In these sizes they will almost certainly come with rim flange protection, too. Tyre reviews are subjective and many of the people who comment unfortunately don’t have a Scooby doo. For instance, ask somebody who is complaining of tramlining when was the last time they had a four wheel lazer geometry carried out, or when they last checked their tyre pressures…GravelBen said:
The other fairly common result of low profile tyres with soft sidewalls is damaged wheels from the potholes.
I'd go for the smaller, lighter wheels with more sidewall - in fact I did, I'm running my Legacy GTB on 16" wheels now.
Totally agree with Ben here. If you have to have low profiles, you need stiffer tyres to prevent wheel damage. I too am run 16" wheels on a mondeo. It feels so much nicer and got rid of the tramlining.I'd go for the smaller, lighter wheels with more sidewall - in fact I did, I'm running my Legacy GTB on 16" wheels now.
Edited by GravelBen on Saturday 1st November 00:03
Chap I know had 25 section tyres, 18/19" I think on his Audi A6, the ride was awful, it tramlined everywhere and the rims and sidewalls had chunks missing.
I can't remember what the standard tyre setup was but these were fitted as some kind of fashion accessory gone wrong.
VERY expensive too.
On a comfy car you need comfy tyres and that, invariably, means higher sidewalled tyres and smaller wheels.
I can't remember what the standard tyre setup was but these were fitted as some kind of fashion accessory gone wrong.
VERY expensive too.
On a comfy car you need comfy tyres and that, invariably, means higher sidewalled tyres and smaller wheels.
Cheers for the advice lads.
So taking into account things like protecting the rims when they fall into potholes, a higher, stiffer profile on smaller rims is perhaps the best bet. This will keep the handling somewhat sports car-ish (I know it's more of a GT, but it looks sporty anyway, so it'd be nice to live up to that somewhat. If I was so adamant about comfort, I'd bite the bullet and get a C5, which however would be too big for these roads and wouldn't fit into my house without a seven point turn, in & another out...) whilst still hopefully offering acceptable comfort with the suspension in normal mode. I'll also get those black plastic rim protector affairs, unless they're a bad idea do you all think?
I've come in for criticism; the seventeens look daft, owners say. I disagree. I think they look pretty good; not too small, and besides the brakes fill them nicely.
These 514 style wheels are quite hard to get hold of; I'm not sure if they're lighter than the other staggered seventeens offered, which are actually slightly heavier than the popular 18" rims many Z4s wear...
Aftermarket wheels are a no-no for me after my previous car, although if I could find a nice set of lightweight OEM looking BBS style split rims with the right offset and rim width, I'd bite. No real luck so far; Italian laws forbid us from getting wider than OEM tyres, otherwise I'd go 245 front and 275 rear, to skim over smaller potholes...
So overall; for my driving conditions (mostly town, heavy traffic, hideously bad roads, with a good mix of (expansion joints every 30 feet) motorway miles, lots of high speed runs whenever I can) and style (very relaxed and comfortable around town, but wanting to keep momentum up, and wanting handling on-par with the car's looks) what's the best choice of tyre type? Asymmetrical treads look great but if they tramline, they're out. It very rarely rains although when it does, the right tyres are very important of course. No snow and the temperatures stay well above zero, so summer rubber should work all-year around barring the occasional treat-myself winter jaunt up the chilly mountain passes an hour or so away. I'll probably keep two tyre repair kits in the car for redundancy.
So taking into account things like protecting the rims when they fall into potholes, a higher, stiffer profile on smaller rims is perhaps the best bet. This will keep the handling somewhat sports car-ish (I know it's more of a GT, but it looks sporty anyway, so it'd be nice to live up to that somewhat. If I was so adamant about comfort, I'd bite the bullet and get a C5, which however would be too big for these roads and wouldn't fit into my house without a seven point turn, in & another out...) whilst still hopefully offering acceptable comfort with the suspension in normal mode. I'll also get those black plastic rim protector affairs, unless they're a bad idea do you all think?
I've come in for criticism; the seventeens look daft, owners say. I disagree. I think they look pretty good; not too small, and besides the brakes fill them nicely.
These 514 style wheels are quite hard to get hold of; I'm not sure if they're lighter than the other staggered seventeens offered, which are actually slightly heavier than the popular 18" rims many Z4s wear...
Aftermarket wheels are a no-no for me after my previous car, although if I could find a nice set of lightweight OEM looking BBS style split rims with the right offset and rim width, I'd bite. No real luck so far; Italian laws forbid us from getting wider than OEM tyres, otherwise I'd go 245 front and 275 rear, to skim over smaller potholes...
So overall; for my driving conditions (mostly town, heavy traffic, hideously bad roads, with a good mix of (expansion joints every 30 feet) motorway miles, lots of high speed runs whenever I can) and style (very relaxed and comfortable around town, but wanting to keep momentum up, and wanting handling on-par with the car's looks) what's the best choice of tyre type? Asymmetrical treads look great but if they tramline, they're out. It very rarely rains although when it does, the right tyres are very important of course. No snow and the temperatures stay well above zero, so summer rubber should work all-year around barring the occasional treat-myself winter jaunt up the chilly mountain passes an hour or so away. I'll probably keep two tyre repair kits in the car for redundancy.
About speed ratings; I'd like Y rated tyres since my ego wants its say, 155MPH restrictor-or-not. The car I'm looking at is running 30 or so more horses, the owner says, from the very first owner before him. Probably an aggressive remap and nothing more, and hopefully not a cause for concern. Would W rated tyres make more sense though, since they'll warm up faster?
Is W even the next speed rating down from Y? lol. If I go ahead with the purchase, against my family's wishes, I'll probably end up getting the BMW Performance Power Kit, standard on the 35is, which gives better cooling via a bigger, faster fan and secondary water radiator, probably running on a seperate thermostat. The 35is bigger intercooler is definitely a good idea too if I can find one. Temperatures here can surpass 40 Celcius in high Summer. Not as pleasant as it sounds. The car's sun-reflective seats and steering wheel would be a God-send.
Is W even the next speed rating down from Y? lol. If I go ahead with the purchase, against my family's wishes, I'll probably end up getting the BMW Performance Power Kit, standard on the 35is, which gives better cooling via a bigger, faster fan and secondary water radiator, probably running on a seperate thermostat. The 35is bigger intercooler is definitely a good idea too if I can find one. Temperatures here can surpass 40 Celcius in high Summer. Not as pleasant as it sounds. The car's sun-reflective seats and steering wheel would be a God-send.
I think it looks fine on 17's.
I have a very different car, but I was interested in the difference between summer and winter tyres on my Octavia vRS, which runs on 225/45 R17's. (The summer tyres are Continental SportContact 5's, the winters are Michelin Alpin A4's).
The cornering/steering feedback is worse on winter tyres as it moves around on the tyre blocks- not that it was ever great anyway- but ride improved significantly. I don't think I'd run winter tyres all year round but I wonder if ride comfort would be better on something like an All-Season tyre for a given wheel size, accepting that there's likely to be some handling trade off?
I have a very different car, but I was interested in the difference between summer and winter tyres on my Octavia vRS, which runs on 225/45 R17's. (The summer tyres are Continental SportContact 5's, the winters are Michelin Alpin A4's).
The cornering/steering feedback is worse on winter tyres as it moves around on the tyre blocks- not that it was ever great anyway- but ride improved significantly. I don't think I'd run winter tyres all year round but I wonder if ride comfort would be better on something like an All-Season tyre for a given wheel size, accepting that there's likely to be some handling trade off?
It seems likely that they are stiffer sidewalls but no-one really seems to have chapter and verse on the implications. See earlier thread here
http://www.pistonheads.com/gassing/topic.asp?t=104...
http://www.pistonheads.com/gassing/topic.asp?t=104...
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