Run a mile in tight dress shoes...

[professor]

and then run another in your favorite sneakers and you will understand how i feel today after andrew put on new wheels and tires on my car.

the car feels so different; more planted, more pliant over bad roads, more assured round bends and feels lighter!! i thought i would miss my stock wheels since they are beautiful as is, but i am even more happy with my new wheels and tires. i know they are not the best wheels in the world money can buy nor the best tires for the discerning driver, but from mine, they feel bloody good!! :thumbup:

[larryn]

Congrats! You know you're getting the "Where's the pics?" posts, straight away.. Don't you?

Specs / details on tires and wheels including sizes.

[Swift135]

Tell us more.... what sizes and what tyres? Give a little more detail of how and when you feel the major difference.

[WAY]

Prof, you can't post something like that and not give us details of the brand of tyres, size and the rims. And more importantly, where the heck are the pics?

[BMWDave]

Originally Posted by larryn

know you're getting the "Where's the pics?" posts, straight away.. Don't you?

Allow me....

[professor]

the wheels are the bmw performance wheels and the tires are sport maxx so pictures will not show anything new to forum members, but i'll post some soon nonetheless.

driving the car now feels like i had a suspension upgrade because its feels so much better damped. its a very strange feeling. i had a 120i before my 135i remember, and switching to the 135i i still retained the butt-clenching reflex before hitting a pothole. the expectation of the vibrations being transfered through the chassis and into the body continued. no longer! the car just feels so much more planted. and in corners i tried going very fast (about 80 on one rather scary-tight left hander) and yet the car tracked through it without feeling jittery at all.

[2QIK4U]

Prof, This is great news. I understand there is an 800 gram saving in the switch to the new rims, is this worth the coin or can we put it down to the rubber? Did you also include suspension/shock mod?

Mike...

[professor]

hi mike. yes, i compared the new with the stock wheels and tires by simply lifting them and they were lighter, and, crucially they feel lighter on the car. still working on getting the suspension upgrade that i like so nothing on that front just yet. about it being worth the coin? not from the perspective of someone like wayne. my car, on the other hand, is proof positive that i am the worst person to ask about adding mods that have the performance-worth of coin!

[smarm]

I like the (unofficial) competition you and Wayne are having prof. Only good things can come from it!

[xa-coupe]

if there are no pics it didnt happen !

[Bim135AUS]

Prof, my last car was a 335I sedan and the bump steer on that car as awful-downright dangerous in fact.

I notice with my 135 with stock wheels and tires, that bump steer is almost totally gone and compliance is fine.

But, as you said, you can always improve on everything, can't you!

[Kris]

So its really the tyres that improved the ride it sounds...

[e36chris]

lol

[WAY]

Originally Posted by smarm

I like the (unofficial) competition you and Wayne are having prof. Only good things can come from it!

There is no competition at all. He is building his car into a beautiful road car, I am moving further and further away from mine being a road car. Comfort? What's that? Noises? Who cares? That's my attitute. There are some stuff that we overlap, like the BMW Performance Parts short shift kit, but everything else is taken at a completely different direction.

[professor]

+1. doctor, i am captain slow and he's the stig. i am just happy that andrew caters to both kinds of people!

[AussieRacer]

Originally Posted by Bim135AUS

Prof, my last car was a 335I sedan and the bump steer on that car as awful-downright dangerous in fact.

I notice with my 135 with stock wheels and tires, that bump steer is almost totally gone and compliance is fine.

But, as you said, you can always improve on everything, can't you!

Small correction, I doubt you a talking about bump steer, but rather bumps being transmitted back through the steering (generally called tram lining). Bump steer is a suspension geometry term.

Bump steer occurs as the suspension moves through its travel range. As it moves up and down, the tie rod from the steering rack to the wheel moving doesn't change in length there by causing the tie rod to operate on an arc which in turn causes the toe angle of the wheel to change relative to the normal straight ahead position (and very likely the other front wheel). This can be used to assist turn-in (Ackermann effect), but also can make the front dart about through the transition states. However the position of the wheel in the drivers hand hasn't moved an inch doing this change.

Given my 1er has plenty of feedback through the wheel (tram lining), I'm guessing that is what you were referring. :smile:

[professor]

that's a googly if i ever saw one! help me to understand what you are saying. is it true to say that given that the tie rod's length is constant, the frequency with which the supension dampens has no relation to the rate of change of the toe angle??

[Rephlex]

Prof- I'm assuming the Sport Maxx tyres are conventional rather than runflat? That's the key IMHO.

[cozza]

Hmmm, still no photos?

[d3syd]

Prof, what are is your contingency plan in the event of a puncture?

[smarm]

Can of tyre weld?

[AussieRacer]

Originally Posted by professor

that's a googly if i ever saw one! help me to understand what you are saying. is it true to say that given that the tie rod's length is constant, the frequency with which the supension dampens has no relation to the rate of change of the toe angle??

googly???

Not 100% sure what you mean by frequency.

I'll try to explain bump steer a different way. Imagine you have the car on a lift at workshop. You hold the steering wheel dead straight. Imagine for a minute that you could easily (eg. spring/anti-roll bar provided no resistance) move one or both of the front wheels through its full range of vertical motion. As the wheel went from full droop (hanging lowest) to full bump (pushed all the way up), the wheel would go through a series of states. Those being the camber would change (whilst minimised on most suspensions, it is impossible to completely remove camber change, and it typically goes more -ve as bump increases), and the toe angle would change. Whether the tow angle goes from in to out, or out to in, or any combination is determined by the suspension geometry. The fixed length of steering tie rod is causing the change, and the type of change is determined by the location of the tie rod pickup points, which the suspension designer carefully chooses to tune the handling. If the suspension is moving quickly or slowly, these changes happen regardless, as it is purely mechanically driven.

Hope that makes it easier to understand without drawings.

Anyway this is OT. Was just trying to clear up terminology.