Featured Bst Wheel Autopsy

Discussion in 'Technical Help' started by Sev, Dec 28, 2018.

  1. I've been wanting to do this for a long time!

    I managed to chance across a pair of BST wheels which were sold as damaged - in the interest of science and asking a few questions of the seller relating to the damage I bought them for not much monies.

    As it happens, the rear wheel was actually good, it was only some laquer which had chipped off it following a chain jump but other than that it was all good. Bonus.

    The front was the one which was damaged.

    The initial premise was that the owner had smashed the wheel onto a kerb. The bike had managed to limp home but the tyre had retained pressure, and having had the tyre still on the wheel for over a week without pressure loss.

    On receiving the wheels, I set about photographing the damage.

    I wanted to see to what extent the damage had penetrated and also the feasibility of infiltration and re-moulding to effect a repair if the damage was not severe. As you may have gathered I have great faith in this material.



    The initial visual read shows us an area approximately 90 where there is noticeable cracking of the surface ply and resin matrix.

    A woodpecker test shows that the delamination extends around 100mm either side of the spoke. This isn't readily apparent as the extremities of the delamination the plies are intact save for some resin crack witnessing.

    Unfortunately what is also apparent is a buckling of the composite.

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    On the inside face, the only catastrophic ply failure is on the bead, but not on the tyre seat - which is intact. However you can see either side of it the fibres have taken a massive impact load.

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    I was impressed. I know how much abuse this material can take, and to boot, I know how much abuse these wheels can take. They are pre-preg decent aerospace structural composite (very different to bodywork pre-preg systems) construction and autoclave cured unlike dymag who wet-lay their wheels. It's safe to say that this load was in excess of 3g if not 4 and it still didn't penetrate the main body of the wheel.



    The initial impression was that perhaps this wasn't beyond saving. I could easily repair this sort of damage - and have done. So more closer inspection was due to see if there was anything I'd missed.

    Unfortunately I then noticed more damaged at the spoke. Ok, so now it's a different story. What first appeared as stressed lacquer was indeed distressed resin damage which means that we've seen some high energy loads pass this way.

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    Without knowing the lay-up in this area I was cautious as to how to proceed next.

    As fate would have it, BST popped into work, and I had the opportunity to have a really long chat with them. I have to say great guys.

    Justifiably they were nervous about the spokes. So at this point, I cut out the hub, and handed it back to them and began the autopsy on the wheel.

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    In cutting out the hub I was really pleasantly surprised. It was nicely laminated and well laminated. the material thickness was constant and the ply overlaps were nicely done. There wasn't any detritus in there, nor was there any sign of sacrificial bags or release films. Done right.

    [​IMG]

    Severe impact caused heavy delamination on the surface ply - christ you might think...

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    The extent of damage was a nice clean split:

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    This is good for many reasons, but the one you need to know is that there's a sacrificial ply in there. This is engineered to take the brunt of the force and intentionally fail before the rest of the wheel gets blasted. Testament to that is the fact that they still allowed the tyre to hold air.



    Chopping a section through this bit, we see where the brunt of the impact was and again, the laminate has done a good job of absorbing the worst of the energy from the strike.

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    The spoke areas itself though was the bit that made my little heart jump for joy... apart from surface damage to some resin and lacquer there was no internal ply delamination

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    I draw your attention to the stripe that you can see in a different shade that permeates the stratified plies. This is unidirectional material, the structural heartwood if you like of the layup.

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    Summary

    The wheel itself despite suffering massive impact was at its most critical structural point still capable of and had survived, and that's great news for anyone thinking or worrying about whether BST rims are a good idea or not.

    I'd have happily gone ahead and repaired that rim, and albeit it would have been a very long and involved repair, I'd have still been happy to put my faith in it.

    Would I say to you guys go and do it? - of course not. But i'd definitely rate these BST hoops over a dymag in the event of a running out of talent situation.

    Dymag take a slightly different approach where they have put a weakened bead structure in. It's designed to collapse on taking damage with the intention of causing intentional deflation of the tyre, whereas BST have adopted the visual failsafe approach in respect to ensuring that damage to the rim is visibly apparent so forcing you the owner to seek advice. They both achieve the same end, but I like this approach better as there's no fudging that the wheel has taken damage.

    They're not only TUV rated but also certified for Japan, so meet the same stringent requirements as the OEM wheels.

    [​IMG]

    :)
     
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  2. Nice write up and thanks for taking the time out to do this...
    Just a quickie, my BSTs are date stamped 2002. They look perfect and unmarked but is there a such a test as the one they do for the mag rims to check for structural integrity? I believe that this carbon fibre doesn’t deteriorate over time but would be worthwhile knowing...

    Thanks, Ian
     
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  3. Very useful and informative write up Sev...I had a pair of Dymags on my T9 which i bought in 2017 they were dated 2003 or 4 cant recall the specific year, however i was concerned about the structural integrity of them because of their age, i emailed Dymag with the serial numbers etched on the inside of the rim outlining my concerns and got a very detailed report on my actual wheels, i was also assured that they would be fine ,and that they do not deteriorate over time....they made an unbelievable difference in the handling of the bike BTW.
     
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  4. thanks Ian. :)
    Your wheels should be fine and will last pretty much a lifetime. Carbon as a material is actually very hard wearing, and the structures don't really degrade over time if they've got the right UV coatings and paints over them, which yours have. they'll have a record of your wheel, just give them the serial number.

    Visual carbon used to get affected by blooming, which is where the resin used to get attacked by UV and go a bit milky over time. then people started lacquering it and was fine.

    Now paint companies will actually make clear primers for just this sort of application whereas years ago they would have just keyed the surface up and lacquered over that.

    bike wheels as well don't get the loads put through them that a car wheel will get so by virtue they get an easier life anyway.

    Advanced composite structures can and do fail, but that won't be age related it'll be fatigue and damage as this one was.
    The aerospace/aviation industry has put their faith in it, and their testing regimes and continuous monitoring protocols are taken to the enth degree. By comparison we may think we put it through some abuse but in reality our applications don't see a fraction of the stresses that a spar on an aircraft will see. However like amy applications where the cost of catastrophic failure doesn't bear thinking about, these industries will retire and replace long before they need to.

    You have to think that there are aircraft, racecars and supercars out there with carbon dripping off of them and they're still going. I could show you some truly dog rough examples to look at but structurally they're sound. Biggest problem the composite industry faces at the moment is how the hell to recycle the stuff -there's only one guy in the UK at the moment that does it iirc, and he collects up, burns the resin off till he's basically got massive piles of fibre and them grinds it all up.

    In early two thousands we were prototyping the bodywork technology for the mac merc SLR. we had a trial tub monocoque which we were ordered to scrap. The natives down in portsmouthstan got their caveman on and decided that the best way to break it up was to use sledge hammers. - Works on cars innit.

    Six of them with massive sledge hammers were beating the shit out of it for over half an hour with barely a dent on it other than some chipped resin and one crack on an area at the front which was a 2mm thick sliver. Oh and a written off windscreen as he smacked it, and the thing just sprung back out of his hands and landed on his no longer mate's car!

    Structural composite stuff like your wheels are a world away from bodywork system materials which are engineered to cure without autoclaves and not witness in the heat and allow the fibres to read through. It's not like say an old corse set of mag wheels or such where it was only ever lifed for one season and twenty years later the now owner an't understand why it's corroded to buggery.

    As it so happens, should it come to that point where you do need to replace them, its the hub they look for when repairing or replacing, they put the machined hub onto a new hoop for you for reduced cost as you've already bought from them.

    For me the thing that really shone was their enthusiasm for what they're doing - they genuinely want to make a good product, and a product that is centric to rider safety first, and if someone has a set of BST's they just want to keep the person happy and riding on them hence offering the replacement service.

    I asked them why it took them so long to make a composite hub as they have on their latest wheels, and the answer was that they genuinely didn't believe the market was ready to accept it.

    They felt they had to build their credibility and faith in the tech before they could get people to buy into it.

    There were some carbon frame blade specials and a 916 carbon framed specials I remember seeing in the early days of 90's performance bikes mag, and that was done by a guy called Gary Turner who is now the MD of BST - and he owns a britten V1000 - naturally I messed messen on hearing that.

    Audi involvement would have meant that choosing them as supplier of choice for the SuperLeggera wasn't taken lightly.
    It was the same as Mercedes putting their faith in Mclaren for the SLR, a small tiny supplier who make stuff out of a material made from fairy dust and pixie tears as far as they're concerned.

    They spoke about the size of that task and of little things like engineering the swingarm. The race team (he didn't say if it was SBK or MGP) got hold of one, played with it and just changing various material specs on the engine cases induced harmonic chatter in the arm at vMax , so armed with that they had to go back to the drawing board.

    Even though the customer profile was perceived as not being at risk of such a thing (collectors, high net worth individuals etc) they couldn't take the risk and so revised and played with the layups to accommodate the one 'what if' possibility. :)
     
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  5. excellent work..
     
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  6. Interesting article. I believe that the first use of carbon fibre wheels on a production vehicle was back in about 1971 ish on a Citroen SM.
    I worked with it on Harriers in the RAF.
     
  7. [​IMG]
     
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  8. Mate, brilliant! Thanks again for your time! :upyeah:
     
  9. Wish blackstone tek would get a set built for the ducati-enduro. Although now with the carbon (blue) ink coming out it would suit me better. Great share Sev'
     
  10. What about the impact of heat for example tyre warmers? I know BST say its ok up to 80 degrees,,,
     
  11. Great article, thanks for that.
     
  12. Very interesting read and certainly gives another perspective on BST wheels :upyeah:
     
  13. Absolutely excellent stuff .. thanks muchly.
    That is the sort of insight that you simply cannot normally get.
    Invaluable, even to an owner of a pair of Dymag wheels, such as myself.
    Double thanks.

    I could say that I went for the Dymags because I thought that their tapered spokes looked like the stronger (and more aesthetically pleasing) design, to my eye.
    But in fact it was probably more down to the massive price drop due to there being "cosmetic defects" (which I can't spot ... a sales ploy perhaps ?).

    A (simple) thought on using alloy hubs .. its probably of little consequence weight wise, as the hub rotates its mass at a very small dia.

    I can certainly concur that the effect of fitting such lightweight wheels is staggering.

    The only downside is that tyre changing is now a diy operation as I dare not trust the job to anyone else .. but that's no biggie.
     
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  14. May I ask, what kit do you use to change your Dymags?
     
  15. Hands would be best...after breaking the bead with a bought or improvised bead breaker like someone made on here from wood...tie wraps to remove, Gafa tape to fit.

    Lovely write up Mr Sev :heart_eyes:
     
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  16. Wonder if there are any January sales on BST wheels...
     
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  17. Shut it.

    Thanks.
     
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  18. Yep, I use hands .. and the cable tie method.
    Occasionally I may also add a very slight tweek with a pair of 3 inch plastic bicycle tyre levers, but they're not really necessary.
    It works like a charm.
    At first I used an improvised bead breaker but I later invested in an Abba bead breaker .. which I rate very highly for shed use, compared to all other types available. They're cheap too, and easy(ish) to store.
    Breaking the bead is, in fact, sometimes the most difficult bit.
    And you usually need a compressor with a fairly decent blast to re-seat the bead (though I did get lucky with a footpump once).

    One very slight disquiet that I did have with carbon wheels was whether they would degrade in ultraviolet light when used in the long term (the bike is a keeper).
    Being perhaps (very) overcautious, I nearly had them painted .. despite that covering up the lovely weave pattern.
    But I couldn't do it in the end.
    Then again, mag wheels don't age comfortably .. possibly a fair bit worse in fact.
     
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  19. Thank you! Will look at the Abba bead breaker.
     
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