Wednesday, August 23, 2006

Tubeless ACX's

A few wks ago I decided to try converting my hoops to tubeless (clicky here) not least because I was curious to see what all the hype was about. Reportedly tubeless boots offer;

  • Lower pressure = better grip
  • Zero pinch punctures - not that I've ever had one mounted on a fully
  • Lighter = easier pedalling
  • Puncture resistance - not that I get as many as the Westoning posse
But I also;
  • Wanted more robust tyres for Afan
  • Had a couple of rim conversion kits lying - DT's own (Eclipse system)
  • Already have tubeless compatible tyres
Being the cautious type I initially set about converting just the front wheel, which in hind sight was a good choice given the number of problems I initially experienced...

The first step required the removal of the current boot (Racing Ralph), the tube and rim tape followed by a quick wipe to clean up the rim.

Now carefully and evenly apply a length of double sided sticky tape (supplied) onto the rim and firm into position. Slice out a hole for the valve and securing the natty tubeless valve betwix the new tubeless rim strip and the rim - starting off bout#1 of the wrestling match. It's quite a challenge to get the slightly elasticated rim strip installed inside the rim, not least because it's tight, the double sided tape conspires to irritate and the blasted strip always wants to twist :x Holding a section off the rim and inserting a small bar/shank of a screwdriver allowed me to correctly align the strip, un-twist and acquire an even pressure all around.

There's no need for a tube ;) so it was straight on with the tubeless tyre, a Bontrager ACX. I already knew that these boots were a tight fit on my DT4.1d rims and my fingers were soon aching with the strain. A few more minutes with the tyre levers...and it snaps! into position, phew.

A couple squirts with the trackpump had the tyre pop into a decent position on the rim but air seemed to be gushing out somewhere. It appeared that my old tyre had taken a number of punctures...but I figured that the tubeless sealant would take care of them, right? So I popped out the valve innerd's, added 40ml of the Bontrager specific Super Juice sealant, replaced the valve and whack'd 50psi back in. Before franctically spinning the wheel and hearing the leaks stop, a little...

Over the next few days I gradually managed to get the tyre to hold at least some air overnight by shaking violently and leaving the wheel on it each side(s) to help the juice find all the tiny holes in the semi porous sidewalls (perculiar to Bonty's tyres and part of the reason why they're so light). A couple of short test rides seemed to be ok but for the relatively low pressures (approx 15psi = dodgy steering!) and having the tyre sealant ocassionally pi$$ all over you before it seals up again, was an...interesting experience.

At this point it became obvious that the old tyre needed patching (yes, just like typically tube) but the number of damp patches on the very thin sidewalls prompted me to acquire a new set of boots. At certain points you could almost see the tyre carcass which was surely a bad thing.

When a new pair of boots arrived I was intreagued to find that the same supplier of the same initial order had this time sent boots that were quite different.

They didn't have the Gumbi dual compound logo (but seem as soft), were heavier by approx 150g ea (around the same as a lightweight tube) but more importantly they had much thicker sidewalls. Not only that but I was relieved to find that these are sooo much easier to install and can be easily "fingered" into place :p

I was so impressed with the replacement and how effortlessly it kept air that I decided to convert the rear wheel at the same time. This was slightly risky as I'd tried installing this second tubeless rim stip on the front, when it had snapped!!! However, my trusty two part, glue absolutely anything adhesive seemed to be holding up well after thoroughly curing for a while. I managed to wrestle the strip into position, un-twist and even out the pressure without the repaired join parting company. The rear installation was so speedy and trouble free compared to the first, but then isn't that always the case once you've learned a few tricks.

Before a visit to the Peaks I figured I'd best test the new installation and iron out any wrinkles. Not wanting to upset the seal rim I decided to leave both hoops at 50psi - which is waaay more than my usual 30/40psi fr/re. At first it felt odd to be back on treaded boots again (the RRalphs are very nearly slicks) and even though they were hard, they rode ok - on hard pack. However, once I got off road I bounced off every root around Woburn :x "I hate hard tyres". I resisted the temptation and completed the ride, checked 'em the next morning and they were still rock solid :thumbu

In the Peaks, I was glad that I'd eased the pressure down to more manageable levels when we started riding the incredibly gnarly, rocky terrain. If I'd have left them hard then they'd certainly have ping'd me off every rock and I'd probably have a bunch of bruises to show for it.

As I was previously riding with mighty rapid Racing Ralphs, I can't say that they're lighter or spin up to speed any quicker. However had I already been using these ACX's with tubes and then converted them I'm sure that I'd be able to feel then accelerate quicker.

The conversion is relatively painless provided you ensure that your tyres are in good shape. Sealing time can be greatly improved by not just spinning the wheel but shaking it side to side, all the way around and leaving them on their sides seems to help too.

In use, I've found that these tubeless boots feel kinda odd and quite different to using tubes, - almost although you're running too little pressure. But a quick look at a weighted tyre doesn't show them to be soggy. I wonder if this "floated" feeling is due to the lack of support and additional rubber that using an inner tube offers? Don't get me wrong, they're not bad and steering is still ok. They just feel different. Perhaps I can run these tubeless boots a bit harder than I'm used to with tubes?

They handle rocky terrain extremely well, you can almost feel the tyre deform and mould to those odd shaped rocks that are resolutely trying to dump you on your butt :p


Farqui said...

Over the months I've been running tubeless I've noticed that although the Bonty Super Juice doesn't dry out but that the tyres need regular topping up - loosing approx 5psi a week. Whereas the DT sealant supplied in their UST kits and JRA's Wheel Milk coats the inside of the tyre with a latex like skin, leaks air less but tends to dry out and need a few cc's adding periodically. Swings and round about's I guess.

Oh yeah, has a great set of vid's that have tips applicable to all UST systems.

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