Chris`I Posted December 19, 2008 Share Posted December 19, 2008 Right, I get what you mean now. You're on about keeping the rolling radius of each corner the same as stock, which is essentially what we've been saying as well. I've never personally heard the difference between front RR and rear RR referred to as stagger, that's normally used for the differing widths, I think that's where the confusion crept in. You're quite right though, the most important thing is to keep the RR as close to stock as is possible, which is why when you go up in width you may need to drop a profile. Kind of. From what Phils explained to me, it doesnt matter if your RR isnt the same as stock, as long as the difference or ratio between the front and back is the same. Mine are smaller RR than stock, but as I keep the ratio front to back, the TC is fine. If you think about it, it works by measuring the difference in speed between front and rear. If you keep the ratio the same, it doesnt matter if the wheels are bigger or smaller than stock, it just thinks you are going quicker or slower than you really are. So when we say you need to keep RR the same as stock, thats not strictly true. You need to keep the ratio of RR front to rear the same +1 although a bit simplified.... Well it is the weekend and Chrimbo holidays too, so my brain has turned off a bit Quote Link to comment Share on other sites More sharing options...
nate247 Posted December 20, 2008 Author Share Posted December 20, 2008 I start work tonight at 6pm until midnight. Funny is that i am over the Kingswood way Saturday but that will be in the wife's astra with all 4 of us.LOL Will have to make it another time now, ie xmas getting in the way. Thats a shame... well your more than welcome anytime buddy. Be good to put a face to the name and take a peek at your Z :-) lol RE this whole traction control issue. I have been reading the responses and trying to get my head round the best way forward (which seems to be change the rear tyres). However before I do anything, I just want to explain through an episode I had with the car this evening first of all, because I am still not 100% in terms of whats going on. I was driving along a duel carriageway this evening in what Top Gear call "mildly moist" weather. Things were going great, got to a roundabout, went straight over on to another stretch of carriageway. Doing about 30mph, put foot down, traction control kicked in. Lifted off throttle for a second or two, press down again, light on and engine cutting speed. Did this same thing about 4 times whist people were closing up behind me. Lasted about 15/20 seconds in total... At times I was lifting then slamming foot down but I was also trying to lift off and feather the power back down but still the light flickered and engine refrained me from progressing. Its beginning to become a real pain the more I drive the car now and in my mind, the variation in which I tried to get out of it, can't mean that its just the wheels spinning / slipping causing this. Presumably (reading between the lines), what some of you are saying is that the rolling radius of the tires is causing this and perhaps has closed the trigger point down from a big(ish) margin for slide, to right on the cusp so any little slide of slip triggers very quickly on the traction control to to the wrong RR / tyre size? Hope that makes sense and likewise shed's a little more info as to the problem I have. Thanks so much again for all the help... as per usual you've all been great in explaining things to a relative car DIY novice lol... Quote Link to comment Share on other sites More sharing options...
Pimm Posted December 20, 2008 Share Posted December 20, 2008 And i thought i was the only one on here LOL. Just got back from work, 1 stella and wasting a little time. Are you around mid afternoon Nate ?? Quote Link to comment Share on other sites More sharing options...
nate247 Posted December 20, 2008 Author Share Posted December 20, 2008 I just can't seem to sleep much before 2am at the minute buddy, so get on here to try and tire the ol eyes... Im free and available tomorrow if you had something in mind. Got a small amount of Crimbo shopping to do whilst the GF is at work, but that can wait as I didn't really want to do it anyway lol Quote Link to comment Share on other sites More sharing options...
Pimm Posted December 20, 2008 Share Posted December 20, 2008 I just can't seem to sleep much before 2am at the minute buddy, so get on here to try and tire the ol eyes... Im free and available tomorrow if you had something in mind. Got a small amount of Crimbo shopping to do whilst the GF is at work, but that can wait as I didn't really want to do it anyway lol PM SENT Quote Link to comment Share on other sites More sharing options...
nate247 Posted December 20, 2008 Author Share Posted December 20, 2008 Received Quote Link to comment Share on other sites More sharing options...
Chris`I Posted December 20, 2008 Share Posted December 20, 2008 Presumably (reading between the lines), what some of you are saying is that the rolling radius of the tires is causing this and perhaps has closed the trigger point down from a big(ish) margin for slide, to right on the cusp so any little slide of slip triggers very quickly on the traction control to to the wrong RR / tyre size?.. Thats what I was gunning at. Usually theres a stagger in RR front to rear. If you've closed that up, it may think the tyres are spinning even when they are not. I'll go bash the numbers into the tyre calc and report back Quote Link to comment Share on other sites More sharing options...
Chris`I Posted December 20, 2008 Share Posted December 20, 2008 OK, I hope this goes to show why you are having problems. Remember in simple terms TC determins slip by seeing the rear wheels spinning quicker than the front (in reality a ratio of this is used to calculate it as the tyre sizes are staggered - and it can do this within a certain margin too, doesnt have to be exact - just close) OK, so taking Rays, my Rotas (which I know are good), and yours and then what I think you should run to get as close to stock as possible with your given width of tyre- Rays: 225/45/18 245/45/18 Diff = 2.73% or 18mm RR My Rotas: 245/35/18 275/35/18 Diff = 3.34% or 21mm RR Yours 235/40/18 265/35/18 Diff = -0.31 or -2mm RR Recommended 235/40/18 265/40/18 Diff = 3.72 or 24mm RR (** Note 45 profile on both gives a bigger diff, hence why I went smaller RR than stock. **) Given that your sizes already put the ratio into negative figures its not too hard to see why TC is kicking in almost instantly. Any time the rear wheels go a fraction quicker than the front the TC will kick in which is what you are seeing. Hope that helps. Would be good if someone validates my results, its the weekend and early for my head Another thing to note, which I'm not sure is true or not, is that if you have a bigger back tyre (ie make the RR of the rear tyre larger), the TC will kick in less as it thinks that the rear wheel is turining slower than the front in relation. So therefor the rear wheel will need to go considerably quicker than the front (ie more spin) before it kicks in. Not sure if you go too far it will break the other way as it thinks the rear wheel is going too slow?! Quote Link to comment Share on other sites More sharing options...
nate247 Posted December 20, 2008 Author Share Posted December 20, 2008 It does make sense thanks buddy and I really appreciate the effort in doing the calculations for me. It seems to make complete sense now as it always happens under acceleration and that must mean that as I am accelerating, the tires are slipping "slightly" but enough to cause the traction control to kick in due to the margin for it not too being so close to the bone. So what are people's thoughts in which case on what to do? Sell the nearly new current tires for a few pennies and get some new ones, or sell the alloys and tires and go the whole hog? Also any recommendations on what tires are best for the Z? Many thanks, Nathan Quote Link to comment Share on other sites More sharing options...
Adriank Posted December 20, 2008 Share Posted December 20, 2008 All you need to do is repalce the rears with any half decent 255/40/18, and that should solve all of your issues. I have pirelli P Zero rosso's on mine in 255/40/18, but they are quite expensive. Any tire in that size should fix your issue. Personally i WOULD NOT fit 265/40/18 on the rays, the wheel itself is not wide enough and it wiull look stupid IMO lol. Quote Link to comment Share on other sites More sharing options...
Greekman Posted December 20, 2008 Share Posted December 20, 2008 OK, I hope this goes to show why you are having problems. Remember in simple terms TC determins slip by seeing the rear wheels spinning quicker than the front (in reality a ratio of this is used to calculate it as the tyre sizes are staggered - and it can do this within a certain margin too, doesnt have to be exact - just close) OK, so taking Rays, my Rotas (which I know are good), and yours and then what I think you should run to get as close to stock as possible with your given width of tyre- Rays: 225/45/18 245/45/18 Diff = 2.73% or 18mm RR My Rotas: 245/35/18 275/35/18 Diff = 3.34% or 21mm RR Yours 235/40/18 265/35/18 Diff = -0.31 or -2mm RR Recommended 235/40/18 265/40/18 Diff = 3.72 or 24mm RR (** Note 45 profile on both gives a bigger diff, hence why I went smaller RR than stock. **) Given that your sizes already put the ratio into negative figures its not too hard to see why TC is kicking in almost instantly. Any time the rear wheels go a fraction quicker than the front the TC will kick in which is what you are seeing. Now you are making sense Chris....(me Chris as well)...and i would like to say again that the car is equipped with ESP...thats why it has got front and rear lateral acceleration sensors as well... the problem is the rear 35 profile to the front 40. If both 40 or both 35 there should be no prob... ESP is not set for different profiles as in other cars that come with different profiles in stock versions....*(check 911's. maserati's, ferrari's) I do believe tho that things are getting worse cos his tyres are not in good condition too and they dont offer good traction during acceleration...on damp roads if i go hard on the accelerator in second gear my ESP will kick in....if i go steady it accelerates really fast....a way to check it out is with the ESP off on a str8 line.... how much wheel spin do you get if you accelerate hard in second gear and how much smoothly...? If the rear wheels are loosing grip like mad then obviously there is a traction problem as well... Cant think why somebody would use 40/35 profiles...its not that it will look nicer....it will sit more on the back.... Anyway....lots of tyres out there depending on the budget... my michelin ps2s are brilliant but the priciest....although on a dry track i would prefer some stickier toyos... in any case anything is better than the mama potenzas!!! Quote Link to comment Share on other sites More sharing options...
Chris`I Posted December 20, 2008 Share Posted December 20, 2008 Cant think why somebody would use 40/35 profiles...its not that it will look nicer....it will sit more on the back.... I've seen it done a few times. Mostly by tyre fitters that dont seem to realise that there is a front to back stagger in rolling radius and therefor make the front and rear tyres the same rolling radius. Very silly when you know how it works, but I guess most cars have the same rolling radius front and rear. Quote Link to comment Share on other sites More sharing options...
adncd Posted December 22, 2008 Share Posted December 22, 2008 why dont you turn the esp off and drive without it untill the tyres wear down, if your not silly, you will drive better and get the benefit of the tread rather than waste them, also it should improve your driving rather than being heavy on the accelerator and relying on the esp to save you when you do get the thing sorted out. Quote Link to comment Share on other sites More sharing options...
Ekona Posted December 22, 2008 Share Posted December 22, 2008 He's already spinning the wheels too much with the ESP on, I don't think turning it off is a great idea in this weather. Nathan has said as much already in his first post, and I would agree with him that that's definitely the safest course of action. Quote Link to comment Share on other sites More sharing options...
adncd Posted December 22, 2008 Share Posted December 22, 2008 but if the ESP is causing it to be a dog to drive, turning it off will probably make it a bit easier. The ESP kicks in early enough without issues so if he can stop it effecting the handling when the car is not realy out of shape and its more of the sensors kicking in rather than the car skidding. it's up to him whether he tries it or not. with regards to your comments on the weather, traction control actually makes a car harder to drive in extreme slippy condition, it overides the controls too much. Quote Link to comment Share on other sites More sharing options...
Ekona Posted December 22, 2008 Share Posted December 22, 2008 If you're used to the car, yes. Mine used to kick in all the time when I first got the car, but now it's only vary rarely on the odd occasion that I even bother having it on. Having driven in this: I'd say that it makes no difference in seriously heavy rain whether the ESP is on or off. On ice or snow however I couldn't say, as I've never driven my car in those conditions. Quote Link to comment Share on other sites More sharing options...
Chris`I Posted December 22, 2008 Share Posted December 22, 2008 but if the ESP is causing it to be a dog to drive, turning it off will probably make it a bit easier. The ESP kicks in early enough without issues so if he can stop it effecting the handling when the car is not realy out of shape and its more of the sensors kicking in rather than the car skidding. it's up to him whether he tries it or not. with regards to your comments on the weather, traction control actually makes a car harder to drive in extreme slippy condition, it overides the controls too much. I'm inclined to agree. While the weather isnt the best, the TC is kicking in even when the tyres arent slipping, it just thinks they are. Just drive it like a normal car and you should have not probs. Be gentle on and off the throttle and dont hoon round corners and shouldnt even notice you dont have it on. BUT the option I would pick is to bite the bullet and have the tyres changed ASAP. Its a cost you dont want, but its one of the most important things on the car, so I'd take the hit Quote Link to comment Share on other sites More sharing options...
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