Member
Factory spec is for comfort and comfort only. You need to learn about tyres and pressures. Also run same size tyres front and rear unless ou want massive understeerOriginally Posted by legoman67
Member
38-40 psi all round. He wants it to handle not drive like a marshmallow
Fast
While upping the air pressure increases the tires spring rate and reduces sidewall deflection, the contact patch ultimately determines grip. The more surface area that doesn't fold up while cornering, the better. There is a point where increasing pressure is counteractive for the tire compound. Only way to know is to try several pressures.
Last edited by dhurley34; 04-24-2016 at 08:35 PM.
Member
Correct and 32 psi is way too low.
Mild trouser brownage
Guys please just stop it, you are hijacking my thread. I have set my tires to what BMW puts on the door jamb, not too high, not too low. These comments belong in one of any other 10000 tire and handling threads out there, as they have absolutely nothing to do with MY issue that I stated in the OP.
Anyway, I'll hopefully get the car on ramps this afternoon and report back with anything I find, or not.
Member
The BMW front toe spec is .12 (per wheel) +/- .07. So you are still in spec all the way up to .19. I feel .15 hits a sweet spot.
Member
If you can't get your head around how an 8 psi differential between front and rear three is affect your handling then nothing here can help you. You don't have stock suspension so using comfort pressures off a door jamb is illogical yes?
Mild trouser brownage
You seem very hostile, but tomorrow I will set my tire pressures to 38-40 all round as you said. I will report back to let you know if that 8psi difference between front and rear gets rid of my bump steer or not.
I was not able to get the car on ramps today, people just don't keep to their word, especially in Spain.
I will add that i THINK the bump steer is worse when hitting uneven ground on the right side of the car although I will try and confirm this tomorrow or when I get some clear bumpy road.
Member
Frustrated yes hostile no. I deal with stuff like this every day, it's my job not a hobby! And do the pressure cold as driving increases pressure by say 4psi from heat. Over 90% of cars coming into the shop have low tyre pressures, that's one of the reasons. I also recommend nitrogen fill as tyres don't leak down as much and the pressure stays more constant.
Last edited by sprintman; 04-26-2016 at 01:37 AM.
Member
tire pressure ratings are actually based on the weight of the car and tire sizes. Has nothing to do with suspension. The rated pressures will provide optimal (even) tire wear, which in turn provides the best handling(most tire contacting the ground).
Its scary that you claim to be a professional...
BTW: the 6 psi difference is to account for the different tire sizes front to rear....
Last edited by legoman67; 04-26-2016 at 01:38 AM.
Current:
- 09 335i MSport, FBO.
- 98 Euro M3, Estoril Blue
- 04 M3, Carbon Black, 6 Speed Coupe
- 06 M5, Black on Black, Full Leather.
- 73 3.0CS, Tagia Green, 5 speed M30b35 converted
Ex's: 1984 325e, 1988 325IX, 1992 525I, 1995 540i/6, 2002 330i, 2005 330xi, 1992 850i, 2003 330i #1, 2003 330i #2, 2002 330ci, 2004 330ci, 2007 328CI, 2007 335i, 2001 M3, 2006 M5 6 speed
Member
BMW will advise the pressures are for max comfort, I deal with them on an almost daily basis. And any tyre company will say the same. Leave this for those in the bisiness
Member
isnt that what you want in a daily driver?
also, its 'business'
Last edited by legoman67; 04-26-2016 at 01:56 AM.
Current:
- 09 335i MSport, FBO.
- 98 Euro M3, Estoril Blue
- 04 M3, Carbon Black, 6 Speed Coupe
- 06 M5, Black on Black, Full Leather.
- 73 3.0CS, Tagia Green, 5 speed M30b35 converted
Ex's: 1984 325e, 1988 325IX, 1992 525I, 1995 540i/6, 2002 330i, 2005 330xi, 1992 850i, 2003 330i #1, 2003 330i #2, 2002 330ci, 2004 330ci, 2007 328CI, 2007 335i, 2001 M3, 2006 M5 6 speed
Member
No I don't and neither it appears does the OP considering g how much money he/she has spent modifying the suspension, guess you missed that? As for weight an E46 has the majority over ze front wheels, kinda ruins your argument ab ought tyre pressures ..Yes I know how to spell bersiness you try tiping on an old iPhone
Last edited by sprintman; 04-26-2016 at 02:01 AM.
Member
I dont have exact numbers, but i do know that the e46 is very close to perfect 50/50 weight distribution. I also said weight AND tire size.
Last edited by legoman67; 04-26-2016 at 02:23 AM.
Current:
- 09 335i MSport, FBO.
- 98 Euro M3, Estoril Blue
- 04 M3, Carbon Black, 6 Speed Coupe
- 06 M5, Black on Black, Full Leather.
- 73 3.0CS, Tagia Green, 5 speed M30b35 converted
Ex's: 1984 325e, 1988 325IX, 1992 525I, 1995 540i/6, 2002 330i, 2005 330xi, 1992 850i, 2003 330i #1, 2003 330i #2, 2002 330ci, 2004 330ci, 2007 328CI, 2007 335i, 2001 M3, 2006 M5 6 speed
Member
Smaller on front with staggered rims (bad idea that). So smaller and 8 psi less does wonders for handling yes?
Member
Take some chemistry and physics courses and answer that yourself...
Current:
- 09 335i MSport, FBO.
- 98 Euro M3, Estoril Blue
- 04 M3, Carbon Black, 6 Speed Coupe
- 06 M5, Black on Black, Full Leather.
- 73 3.0CS, Tagia Green, 5 speed M30b35 converted
Ex's: 1984 325e, 1988 325IX, 1992 525I, 1995 540i/6, 2002 330i, 2005 330xi, 1992 850i, 2003 330i #1, 2003 330i #2, 2002 330ci, 2004 330ci, 2007 328CI, 2007 335i, 2001 M3, 2006 M5 6 speed
Such Membr
I don't think the OP is gaining anything from this bickering...Isn't one of the forum rules to agree to disagree?
OP, have you thought (or had someone comment) about changing back to solid rubber FCABs and RTABs? I have always seen varying opinions on the impact to handling that urethane bushings provide.
Let's make this post great again!
Last edited by Doge; 04-26-2016 at 01:27 PM. Reason: Common Sense for President!
Mild trouser brownage
Thanks man.
Changing back to OEM FCABs has been mentioned, but I am not keen on the idea of throwing money at the problem and hoping for the best. My thinking is that while the powerflex bushings could possibly accentuate a problem that is already there, they are unlikely to be the cause. I think that if the polyurethane bushings were to be the cause of bump steer then there would be nobody recommending them, as they would be useless on a daily driver and plain dangerous on a track car.
The same goes for sprintman's recommendation of increasing the front tyre pressures to 38 psi, if the BMW recommend spec for tyre pressures (whether designed for comfort or not) were the cause of terrible bump steer, then anybody who test drove a new E46 wouldn't have bought one, and there would be 1000 threads telling people to change their tyre pressures to fix their bump steer. This isn't the case. To clarify, there is a place to put air in my tyres about 2 minutes from my house, so the pressures I have set are at cold.
Furthermore, my car is a daily driver. I have changed a lot of suspension components but I am not building a track car. The FSD's are comfortable on a daily driver and my springs are OEM sport springs that came with the car. I have not lowered it, and the only 'performance' parts that I've put on it are the powerflex bushings due to ease of installation (I have no press) and longevity.
I am trying to re-negociate some ramp time to make sure the subframe bolts are tight, but I am doubtful that they are loose (I WILL make sure though). If all bolts are tight then I am completely out of ideas, this does not seem like a common problem.
Would a tweaked frame DEFINITELY make itself visible when getting the car aligned? If I understand correctly, bump steer is caused by the geometry of the suspension components, angle of the control arms, length of the tie rods etc. etc. Could it be possible to have some suspension component out of alignment that doesn't show itself on an alignment spec sheet? If this is correct then surely no E46 that hasn't been in an accident would/could have bump steer??
Maybe I'm brainstorming a bit but it's good to run these possibilities/thoughts by the community.
Thanks again for everyone's input.
Rob.
Member
We've confirmed you're an idiot. Now change the front to 39psi and the rear to 32psi and tell us if the handling changes. Probably beyond you but one never a knows....
Take some chemistry and physics courses and answer that yourself...
Member
whatever helps you to sleep at night...
Current:
- 09 335i MSport, FBO.
- 98 Euro M3, Estoril Blue
- 04 M3, Carbon Black, 6 Speed Coupe
- 06 M5, Black on Black, Full Leather.
- 73 3.0CS, Tagia Green, 5 speed M30b35 converted
Ex's: 1984 325e, 1988 325IX, 1992 525I, 1995 540i/6, 2002 330i, 2005 330xi, 1992 850i, 2003 330i #1, 2003 330i #2, 2002 330ci, 2004 330ci, 2007 328CI, 2007 335i, 2001 M3, 2006 M5 6 speed
Fast
Upon reading your alignment specs, you don't have enough rear toe. Specs are 0.08 to 0.18 with a sweet spot total of 0.26 (0.13 per side) However, I'm not sure this would cause a dramatic bump steer.
Such Membr
Your welks.
I only mention it because I have reads some reviews that "sort-of" substantiate "negative" steering changes with the implementation of urethane.
IMO (not that it's worth much), a tweaked frame should be visible in the alignment specs. Unless, of course, it was slight and the alignment could compensate in which case you likely wouldn't have any bump-steer...IDK...
I would still check the steering guibo as was mentioned, it really does make a big difference if the rubber is loose around those rivets.
I recently had some pretty severe bump steer and tram-lining with a periodic steering compensation visible in the wheel (i.e., I had to have the wheel turned 5-10 degrees counter-clockwise to go straight)...long story short, it was my terrible quality tires about to blow out and uneven wear (you already mentioned yours were newer and not wearing unevenly).
But it does sound similar to my experience...maybe its the rims? Can you get a road-force balance performed? I know an out of balance tire can cause some weird stuff to occur and a spin balance isn't always the best (I am guessing, I am not a tyre tech).
Fast
Whether it be from a bent rim, a wheel/tire combo that wasnt indexed properly, or other anomoly, road force balancing evens out spring rate differences in the sidewall of a tire to eleminate unwanted vibration or feedback. I would not suspect this being the issue since the handling problem is bump steer.
Such Membr
That makes sense, I was supposing anyway.
Thank you for correcting me yet again!
Last edited by Doge; 04-26-2016 at 11:39 PM.
Fast
OP, when you say the universal joint in the steering column was replaced, are you referring to the rubber coupling or the actual collapseable steering shaft with the u joint in it?
Posting Permissions
Reply With Quote
Bookmarks