Tyre report

[jas278]

Subject: Tyre Report

A long story but here is a factual report on 4 tyres which belonged to me .....

Report on 4 Tyres:

branded

‘BRONCO’ Grizzly Claw

Ref: SAG / 05 / 12 / LTS

Ref: SAG / 05 / 12 / LTS

Report prepared for

Marcus Sabin,

Leicester Trading Standards

Report prepared by

S.A. Green – HND, ONC.

INTRODUCTION

I am currently employed by ‘Starco’ Europe, which is part of the ‘Scandinavian Tyre and Rim Company’, as Technical Director. In addition to my responsibility for technical matters in the UK, my role extends to technical support for all 13 plants around Europe and Russia. The Company manufactures wheels, tyres and wheel assemblies for supply as Original Equipment to vehicle manufacturers. Previously, Goodyear had employed me for fifteen years until May 2000. My final position as Technical Training Manager, gave me responsibility for all Technical Training of company personnel operating throughout the UK, Europe and the Middle East. Prior to this position I was Manager of Product Performance and Service department for six years until 31st December 1994. In this role I had occasion to examine many thousands of tyres having failed either in service, or as a result of systematic destructive testing.

I began my career with British Leyland as an apprentice and gained extensive experience in all aspects of automotive engineering in both design and practical skills. I hold an HND qualification in Mechanical Engineering and an ONC in Electronics. Following my apprenticeship I worked for 11 years in research and development, specifically dealing with axles, brakes and suspension systems as part of a vehicle design team. I specialise in all aspects of vehicle design and behaviour, and in particular, tyres, their performance, and the interaction between tyres and vehicle suspension design.

I have been asked to examine the subject tyre(s) with the purpose of identifying the reasons for their current condition, the nature of any structural failure and any possible implications to the merchantable and safe condition for sale. I was given the information that the wheels and tyres were fitted to a ‘Landrover Discovery’ 4 x 4 vehicle and had only travelled for a relatively short distance since they were supplied.

THE TYRE(S)

I examined 4off wheel and tyre assemblies at a private address in Hinckley, at the request of Mr Marcus Saban of Leicester Trading Standards, the details of which were as follows:

Tyre size: LT 265/75R16

Service description: 112Q

Brand: ‘Bronco’ Grizzly Claw

TDR: 14mm centre-line – 17mm at shoulder

Production date / Serial No: No markings

Other markings: Retread made in England – conforms to BSAU 144

EXAMINATION

Following a careful examination of the wheels and tyres, the following details were noted:

Wheel Assembly No. 1

The first of four tyres was examined having been fitted to the front of the vehicle, to reveal a structural failure in the shoulder area of the tyre such that complete and catastrophic deflation had occurred.

There was clear evidence of rubber degradation and cracking due to overheating and rubber reversion at the base of the large shoulder blocks and also at the junction between these blocks and the carcass where there are naturally uneven stresses due to the heavy lug design.

The carcass showed clear signs of distress at these same points and had suffered separation between radial cords and also belt edge, resulting in structural failure. The carcass had suffered from severe abrasion and overheating in the shoulder areas as was evidenced by the inner liner condition. I was unable to detect any evidence of a penetration which might have caused the deflation. The deflation appears to have been caused by the break-up of the tyre structure, the evidence of overheating being such that it had occurred over a relatively short distance including the time taken for the driver to pull over and stop when it was realised that the tyre had failed.

Wheel Assembly No. 2

The second tyre, also having been fitted to the front of the vehicle, was also showing similar signs of rubber reversion in the shoulder blocks with some cracks beginning to appear. However, this tyre remained intact insofar as it was still inflated and no major structural failure was immediately apparent.

Wheel Assembly No’s 3 & 4

These two tyres remained in apparently sound and inflated condition.

Balance Weights

The following quantities of balance weights were seen to be fitted to the wheel assemblies, having been balanced by the tyre shop who supplied the new wheels and tyres;

Wheel assembly #1 – 225 grams

Wheel assembly #2 – 200 grams

Wheel assembly #3 – 190 grams

Wheel assembly #4 – 100 grams

TERMS OF REFERENCE

There are standards laid down within European Directives ECE108 / ECE109 regarding the manufacture and testing of such remoulded tyres.

These performance requirements are specifically to ensure that process quality is consistent to the original development of the remoulded product, and that any such product is capable of being operated within the performance suggested by its service description.

The markings ‘conforms to BSAU 144’ are out-dated and obsolete for two reasons (i) They are now superseded by ECE 108 / 109, & (ii) In any event, there were several suffix additions and revisions to BSAU 144 even when it was current, no such suffix is marked on these tyres, this means that these markings were insufficient even when last BSAU 144 was current.

The remoulding processor is totally responsible for ensuring that the carcasses gleaned from tyres having previously worn-out treads, are in suitable condition for both the re-moulding process and the subsequent safe operation with the new re-moulded tread. A further requirement is dynamometer testing (sometimes referred to as ‘drum’ testing) for the required duration to prove that the tyre tread design, rubber compounds used and re-manufacturing process are all of such integrity that they are safe for continuous operational use up to the full load and speeds indicated by that service description.

The above mentioned dynamometer tests are required to be repeated during production runs to ensure that each subsequent batch also complies with the same requirements.

CONCLUSIONS

The tyres fitted to the front axle of the vehicle whilst it was lightly loaded (as was the case according to Mr Stray), would be subjected to a higher load than those on the rear axle due to the un-laden weight distribution of the vehicle, additionally, the steering forces would also load the shoulder areas of the tyres more than those at the rear. This is therefore a fair indication that the loads at the front axle, although being far below what the tyres are able to carry according to their service description, creates the differing results. Both front tyres were showing signs of distress, with one of them having failed completely, both rear tyres being in better condition than the front ones.

The two front tyres showed clear evidence of overheating and rubber reversion in the shoulder areas and as the tyres were not carrying their maximum load, this tends to indicate a small safety margin with regard to heat generation and satisfactory running temperature.

Mr Stray informed me that he had operated these tyres in the same way as on previous sets of tyres and at the same correct recommended pressures for the vehicle, and I am unable to detect any collaborative evidence for under-inflation prior to the complete deflation of the tyre due to the carcass break-up.

The quantity of balance weights fitted would give concern regarding the uniformity of the re-moulded tyres; generally, re-moulded tyres have very good uniformity as the action of buffing off the worn-out tread tends to reduce any run-out within the original carcass. It is interesting also to note that the worst offender in this regard, was in fact the same tyre on the front of the vehicle which had failed.

It would be a matter for further investigation as to whether the remoulding manufacturer has in fact dynamometer tested the original remould design and/or the subsequent production batches, to prove the ability of the tyres to be operated safely at the rated load and speed in accordance with ECE 108 / 109.

These tyres do not carry the required markings to indicate that they comply with the required testing procedures for the above mentioned standards.

It is therefore my considered opinion that these tyres do not comply with the necessary regulations, governing the sale of such tyres for use on the public highway.

Stephen Alan Green – December 2005.

IT DOES WHAT IT SAYS ON THE TIN...

Forums powered by WWWThreads v5.0.9 Pro

© Copyright 2005 Emap Automotive - all rights reserved.

[dollythelw]

intreguing theres no mention of tyre pressure (contributory factor to operating temp) or any indenpendant testing of the wheel assemblies - the conclusion being that the total wheel imbalance was solely the responsibility of the tyres

Im not for or against broncos merely interested in the engineering post mortem

[steve_a]

A bloody good point though in any case is that there was no serial number on the tyres - I might have quick peek at mine the garage.

For any Quality Assured company I would assume serial number marking would me, perhaps not mandatory, but the only way that you meet QA standards for tracking and recall.

The engineer may have ommitted tyres pressures as this could have been modified after removal, I couldn't testify, if I was doing the same statement, about the tyre pressure as was used, only perhaps that this is what it was when examined and this is what is reported by the user. Not that much use.

I'd be very interested in learning how this all turns out as I have just asked for a new grizzly claw to be sent through to me.

I wore the tread of 2 new ones due to a bad (very bad!) setting on my track rod. However they have not failed.

I have always heard the grizzly claws are batch orientated, a few months ago a group of us did a run to germany and a 90 was running them. We kept seeing the lugs come off on the motorway, which might be related to the kind of stress he is talking about.

[BogMonster]

I don't think you will find individual serial numbers on any tyres, but brand name ones certainly have batch numbers. I had to track down a bunch of Avon Rangemasters a few years back which were faulty, and that was all done with batch numbers. No idea how big the batches were though.

[Les Henson]

This isn't the first time that I have experienced poor tyre quality from Bronco. I bought 4 x 235/85/16 Dirt Devils for catflap, they wore out quite quickly, but were an excellent off-road tyre. I assumed the rapid wear was due to the soft compound of the tyre. Anyway - I replaced the rears with same type, and by the time these two had half worn, the side walls had cracked alarmingly. The cracks seen in this picture are down to the carcass.

Les.

[jas278]

From the report............

Mr Stray informed me that he had operated these tyres in the same way as on previous sets of tyres and at the same correct recommended pressures for the vehicle, and I am unable to detect any collaborative evidence for under-inflation prior to the complete deflation of the tyre due to the carcass break-up.

[BogMonster]

I suppose it's partly down to the road conditions here which are probably not unlike what you'd find in bits of Africa, but I have seen quite a lot of tyres fail structurally before the tread has actually worn out. Only the other day I was out in a Freelander with a horrible wobble, and when it went up on the wheels free it turned out that three of the four tyres were out of shape - after only about 4 years and (I think) 20k miles - and they were Michelins.... seen the same thing with BFGs as well, for some reason the AT's often found on the Japanese market Pajeros seem particularly bad for this.

It is one reason I am sceptical about remoulds which by definition are starting with a carcass that is half knackered. Having said that I am still trying to get hold of a set of those Insa Turbo Special Tracks because they are too nice to resist if they fall to bits I'll go back to BFG's.

[jas278]

I will never touch a remould again, but you do get people who swear by them......

[BogMonster]

And people who swear at them

[jas278]

I suppose it's partly down to the road conditions here which are probably not unlike what you'd find in bits of Africa, but I have seen quite a lot of tyres fail structurally before the tread has actually worn out. Only the other day I was out in a Freelander with a horrible wobble, and when it went up on the wheels free it turned out that three of the four tyres were out of shape - after only about 4 years and (I think) 20k miles - and they were Michelins.... seen the same thing with BFGs as well, for some reason the AT's often found on the Japanese market Pajeros seem particularly bad for this.

It is one reason I am sceptical about remoulds which by definition are starting with a carcass that is half knackered. Having said that I am still trying to get hold of a set of those Insa Turbo Special Tracks because they are too nice to resist if they fall to bits I'll go back to BFG's.

No more remoulds here........................

[sgnas]

Mr Stray informed me that he had operated these tyres in the same way as on previous sets of tyres and at the same correct recommended pressures for the vehicle, and I am unable to detect any collaborative evidence for under-inflation prior to the complete deflation of the tyre due to the carcass break-up.

and just what are Land Rover's recomended pressures for Grizzly 265 75s on a Discovery?

I don't think it's in the handbook

[Jon White]

I was just thinking that - 265/75 is a non standard size so what pressures was he running them at?

Report states the tyres showed clear signs of overheating - I was led to beleive that overheating was a classic symptom of incorrect tyre pressure.

I can agree with the out of balance comments though - HFH had a set of 235/85 grizzlies on his hybrid that when spun up on the balancer one casued it to error as it was over 1kg out of balance!!!!

Jon

[Guest diesel_jim]

This isn't the first time that I have experienced poor tyre quality from Bronco. I bought 4 x 235/85/16 Dirt Devils for catflap, they wore out quite quickly, but were an excellent off-road tyre. I assumed the rapid wear was due to the soft compound of the tyre. Anyway - I replaced the rears with same type, and by the time these two had half worn, the side walls had cracked alarmingly. The cracks seen in this picture are down to the carcass.

Les.

A mate of mine (In Wroughton) had a set of the same as Les's on his 90, occasionally if youw ere following him, one of the lugs would fly off and hot your vehicle!

[Daan]

This isn't the first time that I have experienced poor tyre quality from Bronco. I bought 4 x 235/85/16 Dirt Devils for catflap, they wore out quite quickly, but were an excellent off-road tyre. I assumed the rapid wear was due to the soft compound of the tyre. Anyway - I replaced the rears with same type, and by the time these two had half worn, the side walls had cracked alarmingly. The cracks seen in this picture are down to the carcass.

Les.

My opinion is not to use remoulds full stop, looking at this picture and reading the story explains my reasons. Its ok for a trailer queen, but on the road you can never be sure what you get.

Daan

[richard-dangerous]

Not sure about the bit on remoulds I have had blackstar on my 90 for many years and found them to be excellent, i will only be swapping on the D-Lander because i cant get themany more or in the sizes I want.

[AJL]

Buy Cheap Buy Twice IMHO

[Mark90]

Buy expensive and cry when you rip a side wall.

It seems to be the case that some makes of remoulds have many more proplems than some other makes where you rarely hear of failures.

I use remoulds but there is no way I'd have a set of dirt devils, and would be very wary of any other bronco tyres. However I'm happy to use Colways or Fedimas.

[Andy]

i had blackstars, the sidewalls fell apart.

ive got greenways & have replaced two due to damage (not faults just damage)

im happy with remoulds, the way i see it is my tyres seem to die due to damage before they'd wear out anyway so why spend lots on a tyre to break it?

typically damage is stone cuts in the sidewalls or in one case a metal chairleg through the sidewall - yes i was REALLY impressed there. tyre was about 400miles old.

[jas278]

A lot of mixed views , will never go back to a remould ,but I must say there has always been a lot of good reports about Greenways. As for a damaging tyres ,I think the better the tyre (quality) the more it will withstand so a cheaper tyre may well be false economy allround.........

[Mark90]

As for a damaging tyres ,I think the better the tyre (quality) the more it will withstand so a cheaper tyre may well be false economy allround.........

Not always the case, a first gen tyre sidewall will generally cut on rocks as easy, if not easier than a remould tyre sidewall.

I have found BFG sidewalls to be particularly poor with regard to resistance to cutting, where as my remould fedimas have had loads of abuse, tread is well cut up, but the side walls show no cuts at all.

[steve_a]

one factor about going for Bronco tyres, Grizzilies included, is that Bronco is the maker and only seller of the tyre.

I have been waiting since about this time last month for a new grizzy to be sent, despite them taking my cash on the 25th aug. But you can only give them so much abuse before your just left with the option of ditching them and getting a complete new set of tyres.

Only dealt with them once before and they were all right, so hopefully this is just a blip.

Slightly more on topic is that Bronco mention that they had moved factory, so I hope some quality control concerns might be addressed.

[jas278]

Slightly more on topic is that Bronco mention that they had moved factory, so I hope some quality control concerns might be addressed.

Theres a lot more to this story than the tyre report . Ask them why they have moved factory , ask them why they keep telling people different dates , for supply and diferent stories, my expierience of dealing with Bronco has amazed me ? I always find honesty is the best policy... unless you have something to hide ?

[white90]

Honiton Hobbit had Colways fly apart less than 5miles after fitting them

remoulds always a risk IMHO

[jas278]

Honiton Hobbit had Colways fly apart less than 5miles after fitting them

remoulds always a risk IMHO

Well , it just shows whats good for one is n't always good for everyone, of course when you do have a problem its how the supplier deals with that problem , that also has a bearing on the opinion of the product involved. In my case Bronco were n't interested ,its only when I researched tyre regulations that I found the set they had supplied to me did nt meet ECE tyre regs...........