The Law of the Sod

[clivea]

I cannot believe it. I run three cars and today have picked up a puncture in the XC 70. Normally not a problem but it is within one inch of a previous repair, and the repairs would overlap, and V rated tyres can only be repaired once. So on two counts its a new tyre. Why didn't Volvo keep the car's speed down to 130mph instead of 134mph and then she could have had H-rated tyres from new.

Will fitting one new tyre to the rear in conjunction with a part worn (6mm) cause any problems with the 4WD Haldex system, or am I looking at two new tyres. I normally like to keep tyres at an even tread depth across each axle, but this months not a good one for unscheduled expenses!

[tt82]

I believe keeping the tyre treads the same depth was only an issue with earlier generations of the Haldex AWD system, and you should be ok. Maybe somebody else could cofirm that.

[clivea]

Thanks that makes sense as the space saver is some 50 mm less on OD than the road tyres. But I would be limited to 50 miles if using that. The Owners Manual doesnt say anything about running with different tread depths. Luckily I caught the puncture on the drive while doing my weekly tyre pressure check and noticed it had lost 3 psi in a week.

[weedeno belfast]

keep same make should not affect as much because it will be same size side wall (i know everyones going to say but if its a 205/60/15 it is same as the 60 ratio in all tyres ) its not you put two diffrent makes of same size tyre beside each outher there is allowed to be 10 percent diff each way so one will be taller one smaller hence why people say as long as they match on each axle then leads to problems with abs in your case haldex systems

[clivea]

I don't understand how the Haldex knows whether the height difference is sidewall or tread depth? Could you explain please?

[GrantA]

Originally Posted by tt82

I believe keeping the tyre treads the same depth was only an issue with earlier generations of the Haldex AWD system, and you should be ok. Maybe somebody else could cofirm that.

Before I bought my XC70 I did a lot of research on Haldex couplings and failures of the system as fitted to Volvo 4x4 compared to that as fitted to Audi 4x4.

Yes tt82 is quite correct Phase 3 (or Gen 3) Haldex systems as fitted to Volvo have an uprated spline shaft/drive coming out of the gearbox. Previous versions had a "weaker" spline drive and it was so sensitive to differences in the drive train you not only had to have the tread on tyres on the same axle within a couple of mm of each other but the same applied to the front and rear axles. At the time the recommendation was you had to swap tyres front to back if the wear difference was IIRC 4mm or more and if you damaged one tyre and had to have it replaced then you had to replace both tyres on the same axle if the wear was greater than 4mm. And get this, if the 3 remaining tyres had a greater difference in wear than 4mm from the new tyre the recommendation was to replace all 4 tyres - a real bugga. I hasten to add this did not happen to all Phase 1 and 2 4x4 Volvos but it was reported as an ongoing problem hence the rumours about failing Haldex systems.

For those interested this is how the Haldex system works as fitted to Audi, the system is an excellent one, the weakness with the Volvo system was the drive from the gearbox to the Haldex. http://www.vaglinks.com/Docs/Audi/TT...StudyGuide.pdf

[clivea]

Grant, thanks for the info and that is a very good link. My next dilemma is whether to just put on a relatively cheap Hankook ( correct spec) to get me through the next few weeks when I was the considering going for Goodyear Vector 4 seasons. I could then keep the Hankook (off rim) as a spare and bung it into the caravan when we are touring. Although I guess that wouldn't be acceptable to some European countries which I understand require tyres on the axle to be same spec and same make. Might be time to go back to a car with a proper spare which puts me a bit more in control of events!

[cloggers]

Originally Posted by clivea

Although I guess that wouldn't be acceptable to some European countries which I understand require tyres on the axle to be same spec and same make.

This worries me a bit... Could you please specify which countries require this? As I don't want to end up getting fined for having 2 different makes of tyre on my car!

[Philip Fisher]

If it is only losing 3psi in a week and you are skint at the moment then why not just keep pumping it up?

[Philip Fisher]

Originally Posted by GrantA

Before I bought my XC70 I did a lot of research on Haldex couplings and failures of the system as fitted to Volvo 4x4 compared to that as fitted to Audi 4x4.

Yes tt82 is quite correct Phase 3 (or Gen 3) Haldex systems as fitted to Volvo have an uprated spline shaft/drive coming out of the gearbox. Previous versions had a "weaker" spline drive and it was so sensitive to differences in the drive train you not only had to have the tread on tyres on the same axle within a couple of mm of each other but the same applied to the front and rear axles. At the time the recommendation was you had to swap tyres front to back if the wear difference was IIRC 4mm or more and if you damaged one tyre and had to have it replaced then you had to replace both tyres on the same axle if the wear was greater than 4mm. And get this, if the 3 remaining tyres had a greater difference in wear than 4mm from the new tyre the recommendation was to replace all 4 tyres - a real bugga. I hasten to add this did not happen to all Phase 1 and 2 4x4 Volvos but it was reported as an ongoing problem hence the rumours about failing Haldex systems.

For those interested this is how the Haldex system works as fitted to Audi, the system is an excellent one, the weakness with the Volvo system was the drive from the gearbox to the Haldex. http://www.vaglinks.com/Docs/Audi/TT...StudyGuide.pdf

Both my brothers had Phase 1 V70 Cross Country's as they were called then, and both suffered with this issue. Interestingly the S reg one seemed worse than the V reg one, so I guess there was some development of the system. The S reg one would whine going round corners as the system seemed to 'wind itself up' and then the noise would go away when taking a corresponding corner the other way as it would 'unwind'. One of them (the v reg) is still in the family and has done 150k now, but it has had the angle gear, spline replaced at a price which could have written the car off.....