Ekona

There's a lot of conflicting threads and posts on here with regards to the subject of tyres and in particular mixing them on the car, so I've been asked to write this which should hopefully clear a few things up as well as giving you something to think about and make your own mind up on. I'll start with the very obvious: Tyres are the only thing keeping the car in contact with the road. As daft as it sounds it's always worth remembering, as whether you're chasing tenths of seconds on track or munching motorway miles you will always want tyres that give you full confidence that they are doing their job properly at all times and in all conditions. That's the really the key point I'm getting at through the whole of this post, confidence in your car and tyres. If you take nothing else away from this, just remember that stability will lead to confidence and you won't go far wrong. I'll start with an oft-used example of tyres here, the RE040 (left pic) and RE050 (right pic). These are OEM fitment on the DE and HR engined cars respectively, and the latter on the 370Z as well. They seem pretty similar at first glance: Five main bands over the tyre, slots all pointing the same way where appropriate, both made by Bridgestone and only one number apart... Now look closer. See the centre band? On the 40 it's split with a line down the centre, on the 50 it has no line and the cuts into it are much more pronounced. The next two bands out are completely different, look at the angle and sweep of the cuts. Finally look at the out bands, and see just how different the cuts in there are. Two tyres, both by the same manufacturer, both fitted as standard to the Zed over the years, both just one number apart, both completely and utterly different. This is absolutely key in understanding why mixing tyres is a bad idea. I've driven on both of these tyres in the dry, the wet and on track, and they are even further apart than they now look. The RE040s are noisy, uncomfortable, have good grip in the dry but atrocious grip in the wet; The RE050s have a very progressive feel, outstanding water displacement at high speed and excellent dry traction. They're the tyre equivalents of a Ford Escort and a Ferrari Enzo. That said, as long as you keep all four tyres on the car the same (be it all 040s, all 050s, or whatever you prefer) you'll find a car stable and predictable. Now what happens if you mix them... Let's think about this logically. Let's picture the Top Gear test track at Dunsfold as it's a place just about everyone is familiar with, and let's say it's bone dry. Our test car is a stock 350Z naturally, and in the first instance is fitted with RE040s all round. Get in, drive, enjoy. No issues at all, car feels just like it should. After a few laps it starts raining, so you adjust your driving and speed to match. Car feels noticeably slower, tyres have nowhere near the grip you're used to, but nothing feels drastically out of place. Car goes back into the pits, time for a spot of lunch, and ZOMG! THE SUN'S OUT! YAY FOR A DRY TRACK IN THE AFTERNOON! Now we leave the RE040s on the front but put RE050s on the rear. Jump in the car, off you go, giving it full beans. Will you notice any great issues? No, probably not. Remember, both tyres are good in the dry, so you'd expect the car to be fairly balanced. It handles just like it should, but you do notice a bit more traction from the back when coming out of the Hammerhead. Soon the heavens open and the track is soaking wet. Same car, same setup (40s on the front, 50s on the rear), same driver. Once again, you go for a fast lap. First time round is slow as you get used to the wet surface again, then you start picking up the pace as you get used to the conditions again. You come round Chicago and brake hard for the Hammerhead, and start to turn in. The front washes ridiculously wide and you're in the gravel. Why? The RE040s have much less wet grip than the RE050s, and so you get chronic understeer despite the rear feeling very planted. Now we change the tyres around, so that the 40s are on the back and the 50s on the front. Same wet conditions, same driver. Out of Chicago, onto the power, brake hard for Hammerhead, car turns in fantastically well to the left, same to the right, but the second you get onto the power coming out the arse end overtakes you and you're suddenly facing the wrong way. As you've put the grippier tyres on the front the car now wants to oversteer everywhere, and as you carry on round the track and all tyres get hotter the differences become more pronounced. Yes, very huge and over-complicated scenario perhaps, but it illustrates the basics very well. There's a million and one things you can do to adjust grip balance between front and rear (suspension settings, weight balance, tyre pressures etc) but all those things will give you a subtle difference you can learn: Completely different tyres will always behave at such extremes you'll always struggle to cope, and that's on track when you've got the space to get it a bit wrong. Tracks are made of one material and all laid at the same time (for the most part, airfields are a different kettle of fish), and as such you can almost cope with different tyres as the road surface doesn't change. I can't think of too many roads in the UK that are the same! Imagine you're driving on a motorway at 70mph in our mixed-tyre Zed in the rain. You're in a straight line, in all honesty very little is going to go wrong. Suddenly there's a car in front you of that you need to overtake, so you indicate and pull out to the right. At the same time you happen to cross a section of road that has been repaired and replaced so has different grip to the rest. Your axle with 050s on takes it fine but a combination of surface, temperature, camber, suspension travel and steering angle combine to make the 040s aquaplane and you suddenly find yourself in a spin at 70mph in the middle of the M6. Your odds of walking away are pretty slim at this point. If you were on 040s all round you'd know how crap they are in the wet and drive appropriately, but on mixed tyres you don't get that kind of warning as you're getting such mixed signals. It's not a scenario that would happen often, but given the nature of driving would you really want to take that chance? There are so many different variables on a car and we take them all into account when driving, most of them subconsciously, and I simply can't understand why people would want to add another one in there just for the sake of a couple of quid. Let's make no mistake here: Mixing tyres is done 99% of the time because people are too tight to buy the correct tyre. That goes for all other cars as much as it does for the Zed. You need a new set of rears a couple of thousand miles before the fronts, but instead of replacing them all with something different people tend to take the cheap option, and then wonder why the car feels horrible to drive. Driving isn't cheap, I appreciate that, and sports car driving even more so, but is it worth risking your £10,000 car for the sake of a couple of hundred quid? No, of course it isn't and anyone who does so knowingly is an utter fool. If you can't afford to swap tyre brands for something different then don't! Some tyres are better than others but ALL tyres have been through EU type approval, which makes them all perfectly safe to use on the road. A set of Michelin Pilot Sport 2s will be infinitely better than a set of Nankang Ditchfinders, but a car with four Nankangs will be more controllable, more predictable and safer than a car running two of each. There's so much more to it, not least of all different compounds, different thermal expansion points at set temperatures, amount of water dispersed at set speeds... So much detail that you need a degree in physics to understand it all properly. Thing is, common sense is more than enough once you know the basics. I appreciate that there are people out there running mixed tyres who say that it's perfectly safe and they've never had an accident, and good luck to them in that, but I maintain it's always just a matter of time and the wrong circumstances that is going to lead to tears. It might not even be their fault: It might be the idiot that pulls out without looking causing them to swerve and end up in an emergency situation that they have no control over due to mixed tyres. Hell, that could happen even on matched tyres, but I know which is going to give you a more predictable and balanced car to give you the best chance of getting yourself out of any trouble. I'll leave you with a thought: There's not a car manufacturer in the entire world who supplies their cars with different tyres on. Their combined research budget is billions of billions of pounds. There isn't a single professional race series that would ever consider running mixed tyres, and they're aiming for hundredths of seconds so surely if it gave them an advantage, they'd do it. It won't, and they don't.

Update time! Car was back with Nissan today who changed the master cylinder, and whilst the pedal feel is certainly better I'm still not 100% happy with it. I'm starting to wonder of the existing clutch line has started to degrade, so I'm going to order a replacement stainless steel one with Adam @Z1 and see how I get on once that's been changed. At this point I'm not sure if the soft pedal is now partly in my head because I'm looking for it, however I'm so far down the line now that I'm going to carry on until I'm 100% happy with the car again.

If you're braking so hard that you're activating the ABS then you're either pressing the pedal too hard or your approach speed is too high IMHO. Disabling ABS really won't make you any quicker, being smoother will. Sometimes I find the Zed brakes a little over-servo'd and I wonder if it's this that people would like reduced, rather than the actual ABS control itself.

Silly question perhaps, but why don't you just find the nearest Nissan dealer and take one for a drive? At least that way you'd really know what it's like, as opposed to a passenger ride in someone else's car?

Bin the Bose and get a decent head unit.

Embarassing.

Congrats to the team who should be applauded for taking a pro-active stance over this. Well done done chaps.

Love the 928, mate of mine has recently purchased a '79 one that needs a bit of attention. I've had a drive of it and it's a bit of a monster at low speeds and the gearbox needs some TLC to shift, but being able to spin the wheels in 3rd was absolutely hysterical fun! Love them

Why not ask them?

+1

That's the spirit!

Ah, I'm glad you said that about bleeding the air, they took a good couple of hours extra than they said they were going to getting the air out! Any tips I can give them?

My original ESR K1 was a perfect fit on my car.

Oh you definitely convinced me, hence I got Nissan to change the slave cylinder today as you suggested but there's no change in the issue at all, so I thought I'd open it up to the masses as it were. I didn't want to keep running back to you via PM taking up your time if the answer was out there and I'd missed the obvious. Sorry if it came across as me ignoring you, I really didn't mean it to look like that.

I'll try to keep this as simple as I can... In short, when the car has been sitting in stop/start traffic OR if the car is warm and you sit there pumping the clutch pedal in idle, the pedal will go from having resistance from pretty much the top to having no resistance whatsoever until half way down when you start to hit the biting point of the clutch itself. The car has been into Nissan today who have changed the clutch fluid (their suggestion as it was a very dark colour) and also the slave cylinder (my suggestion, after reading on here). On the 45 min drive home just now and deliberately putting the car into queuing stop/start traffic the problem remains. It first started doing this a couple of months ago, and now I can replicate it every time. If I let everything cool down (i.e. 20 min motorway run) it goes back to being what I would consider normal again, but if I work the pedal some more the problem returns. Approximately 3000 miles/4 months ago I had an Exedy clutch and Fidanza flywheel fitted, should this be relevant. The car has now done 28K miles in just under 4 years, including some fairly heavy track work (4 or 5 days in the last couple of years). My gut feeling is that one of the seals on the master cylinder has gone/is going, which would mean that it will seal when cold/warm but when hot or under a lot of work the primary seal is allowing fluid past it, but the secondary seal is still holding and allowing me to give the required pressure to the rod to disengage the clutch and change gear. That said, at this point I'm willing to listen to any ideas before I take the car back to Nissan and get them to change the master cylinder as well. The car is booked in with Abbey end of next week to have them listen to the chatter from the gearbox and flywheel which may or may not be connected to this issue (I'm aware that some extra noise is expected with a lightened flywheel, I just don't know if my noise is normal and have no frame of reference hence the trip to Abbey!). I have an upcoming trip to the 'Ring next month so you can see why I'd like to get this sorted before then...! As always, any ideas or comments are more than welcome.

Looks as good as anything else to me. Doesn't seem ridiculously cheap either.

Oi, why do I get bumped to last when we've got the same numbers??!!

Yes, as well as a billion other Bad Things. Don't mix tyres on the Zed full stop.

1: Dcash 274.4WHP JDM 2-3FIDDY 272.2WHP - VQ35DE 3-GT4 Zed 270.1WHP - VQ35DE revup 4-Andlid 265.4 WHP - VQ35DE 5-Jcor 263.8WHP - VQ35HR (no mods) 6-Clazba 262WHP - VQ35DE JDM 7-Rich5259 257.8WHP -VQ35DE (No mods) 8-IanS16 251.9WHP - VQ35DE JDM 9-rdsprint 252.5 - VQ35DE revup (no mods) 10-Lincolnbagie 250WHP -VQ35DE 11-Ekona 242WHP - VQ35DE revup List edited to make mine seem even more pitiful

I've used it both a day after waxing and straight after, and tbh there's really not a lot of difference at all to the finish.

It's even worse when people assume they need more power to be faster... Try getting some decent brakes, some decent rubber and some driver training and then you'll soon realise that the Zed is more than capable of being quick enough when you get the basics right. Just adding another 100bhp won't suddenly make it leave a decent driver in an sporty car for dust.

BFD If it's a good price for you (and I'm guessing it is), then that's all that matters.

They're spindly and make the brakes look tiny, they're also too big for the car and give it a roller skate look. As ever, opinions will differ of course, variety and spice and all that. I'd disown him.

Can someone please tell the RX-8 owner that they've ruined a very beautiful car with those incredibly fugly wheels If you were a true friend, you'd have told him by now

They can, and they will, but they're completely wrong to do so as our cars are legal in another EU country and not having riveted 'plates doesn't make the car dangerous. Try explaining that to the gendarmerie by the side of the road though...