The Beacon Message Board

Rim split on my low mileage but 15 year old Bike Friday yesterday on the way into Bewdley. I'd not ridden it for a while but hadnt noticed anything after holiday in Derbyshire. I think pumping up the tyres was the proximate cause. Only Avon Valley Cylcery stock these rims and I'm now waiting for next years delivery from US. None of my wheels is new so I'm going over them with a magnifying glass this afternoon.

Let me know if you'd like to borrow my rim calipers if you're unsure of any Dave.

Thanks Steve someone else has recommended using calipers so I'll take you up on that offer and do an inspection one evening.

Steve many thanks for popping the calipers round - really kind of you. I'm guess that these arent the dental ones that someone else recommended although you could take a tooth out with them! The inspection starts tonight on a new rim to set the standard.

They're specifically designed for cycle wheel rims - just run them all the way round the rim looking for the thinnest area - there is typically quite a variation in different positions (both across and around the rim).

I was reading Alan's thoughts on disc brakes and couldn't really believe that he was wearing rims out after only 4,000 miles, but I thought I should check mine just in case. I can't seem to find the wear indicators on the Shimano RS-10s that came with my Genesis, which I bought in July. They've done about 5,000 kms. Is it really possible that they're worn out already, or are the wear indicators just really conservative in order to protect Shimano from getting sued when people have wheel failures (and so that they can sell more wheels)?

Also, Dave and Steve, when you've used the calipers, is there a standard thickness that you regard as a minimum for safely using the wheels?

laurence_cooley wrote:I was reading Alan's thoughts on disc brakes and couldn't really believe that he was wearing rims out after only 4,000 miles, but I thought I should check mine just in case. I can't seem to find the wear indicators on the Shimano RS-10s that came with my Genesis, which I bought in July. They've done about 5,000 kms. Is it really possible that they're worn out already, or are the wear indicators just really conservative in order to protect Shimano from getting sued when people have wheel failures (and so that they can sell more wheels)?

Also, Dave and Steve, when you've used the calipers, is there a standard thickness that you regard as a minimum for safely using the wheels?

Laurence,

As a rule of thumb the braking surface of the rim should be perfecty flat and will tend to wear very uneven and will start to bow as it wears, this will be clearly visable. However, I tend to put a steel rule on edge across the rim surface and in line with the spokes to view the amount of bowing occuring.

Once you can see daylight under the edge of the rule you need to monitor on a regular basis.

As the rim wears it of course gets weaker and usually what happens next is that the pressure of the tyre splits the rim. If your lucky you will see this in plently of time. If your unlikey it will do it while your riding, usually resulting in the tyre and tube parting company from the wheel together with a section of the split rim!!

A tell tale sign is slight clicking noise when braking, this is often the rim starting to split, dont ignore it!!

Open Pro rims dont have a wear indicator either, but the Open Sport rims do.

Yes, I'd held a ruler up to them last night and was worried about how concave they were looking. Incidentally, the Open Pros on my other bike are fine, despite the fact that they look fairly old (I bought the bike second hand so I don't know exactly how old the wheels are).

I think it must partly be due to me using the stock pads on the Tektro brakes that came with the Genesis for a couple of months, and then the stock Shimano pads that came with the better brakes I replaced them with since then. I've ordered some Kool Stop Salmons, but it's looking too late for this pair of wheels.

Answering my own question about what thickness the rims need replacing at, the CTC suggest 1 mm.

1mm is recommended min but I think I've read 0.7mm is the absolute min. However, to go that low you need to be confident you've found the thinnest bit. Whether you can do so depends on the rim and position of your pads. Someone cut across the cross section of a replaced rim and this revealed that the thinnest bit was in the cavity that can't be reached with calipers - still at least a split there shouldn't cause a blowout I suppose.

I wasn't surprised at Alan's 4,000 because I recalled being surprised at how fast I wore my first set of OPs out. However, checking records I find I got 8,000 out of them. That was on standard Shimano pads. My next set have done about the same with Koolstops and I think they're still OK but maybe I should have a close look. A lot depends on what sort of weather and roads you ride on (and we know how much AW likes hanging around fords). However, the Koolstops don't seem to become impregnated with flecks of metal which must add to the wear rate.

You'd be welcome to borrow my calipers if you want to check.

Thanks Steve, but I just ordered some from eBay because I thought it might be useful to have some to hand to do more regular checks. It had occurred to me that perhaps the thinnest point isn't accessible, but hopefully the fact that 1 mm is a relatively conservative minimum takes care of that.

Hmmm, just did a quick finger test on my 8000 mile old OPs. The rear feels OK but the front feels a bit thin, needs closer inspection I think. I'm sure I wore the rear one out first last time.

Koolstop inserts seem to be less aggressive on the rims than some , I've got the duel compound on one bike and salmon on the other.The make of rim or rather the alloy used seems to make a big difference .Makes sense really as the coefficient of friction will vary with metallurgy, Soft metal will grip but wear out quickly. Mavic rims seem to last well.
I've still got a garage full of worn out rims on good hubs, and never know weather its worth replacing the rims or the whole wheel

keith wrote:I've still got a garage full of worn out rims on good hubs, and never know weather its worth replacing the rims or the whole wheel

Unless you have a high value hub it's touch and go whether it's worth having it done commercially but if you're prepared to invest an evening and do it yourself it only costs the price of a new rim. I reckon the lifespan of an average hub and spoke is about twice that of an average rim (and if I didn't have phobia about servicing hubs they'd probably last even longer). The only tool you need is a spoke key and it's strangely therapeutic too.

It's not so easy if they're factory wheels though, from what I've read. It seems near-on impossible to get replacement rims for Shimano or Mavic wheels - at least without spending nearly as much as a whole new wheelset.

laurence_cooley wrote:It's not so easy if they're factory wheels though, from what I've read. It seems near-on impossible to get replacement rims for Shimano or Mavic wheels - at least without spending nearly as much as a whole new wheelset.

Quite so. My policy, therefore: use cheapish but robust factory wheels for 90% of riding and bin them after 2 to 5 years; have a nice set of wheels and never ride them in crap weather and they'll probably last as long as I do.

Having tested nearly all my rims with Steve's calipers I am off to pick up some new wheels from Ben in a minute. I've had rear rims go at under 4,000 miles on winter bikes. I'm switching to rims with indicators and koolstop salmon pads. Alan is dead right about feeling it on the brakes I should have turned around the other week but had a meeting arranged in Bewdley. The concave test is well worth doing too. When I showed a tyre lever to the Bike Friday rim it came away on the other side as well!

Here is a a little video:

http://www.youtube.com/watch?v=bQK762wtpfM

As good and as much as I highly rate the Koolstop brake blocks, (both colours) they are still prone to occassionally picking up lumps of ali swarf from the rims. But no where near as bad as the Shimano ones though!!!

That said, you will always hear it first, its the sound of £'s as your rim is being slowly ground away!!

So they are certainly not a "fit and forget" item, you still need to check for smaller particles of ali swarf on a fairly regular basis, I do mine every week, but then I do have OCD.

Further to Alan's observations about Koolstops or other expensive brake pads, be careful not to confuse improved braking co-efficiency with reduced rim wear. I use the more expensive end of the Aztec range - they do improve braking but do not reduce rim wear or problems of detritus embedding into the blocks.

As an aside, during my days on the railways I once fitted entire rake of Mark 1 carriages with a set of experimental compound brake blocks with a high coefficiency. They were lighter than traditional cast iron, easier to fit and removed the environmental hazard associated with iron dust. They were too successful. When the driver made a normal application the effect was a virtual emergency stop causing chaos in the Restaurant Kitchen withcutlery flying everywhere and staff being propelled involuntarily down the carriage. I kept a rather low profile in the yard thereafter! They also increased wear on the tyres and we had to return to cast iron blocks.

You guys have got me all paranoid about my wheels now, so have cleaned, measured and trued today.

Mavic open pro rims; rim surface slight concaved and can just see a glimmer of light underneath a steel rule. front thickness 1.7mm and rear 1.3-1.4 mm. Guess they are doing ok for nearly 2 years old and about 12,000 miles. Both still almost true as well, just a quarter of a turn on 2 or 3 spoke nipples needed. Bloke that built them knew what he was doing.

Just replaced brake pads too. Koolstop salmon previously, but have now fitted Swissstop. does anyone else fit these? I too clean rim surfaces and brake pad surfaces weekly

Clive wrote: Just replaced brake pads too. Koolstop salmon previously, but have now fitted Swissstop. does anyone else fit these? I too clean rim surfaces and brake pad surfaces weekly

Yes I have tried Swissstop ones and in truth I wasn't that impressed with them, let alone the cost of them!

My own experience was that they seemed to gather as much swarf as the Shimano ones. But perhaps thats just me, as they do seem to get good reviews

Still waiting for Avon Valley Cyclery to get some rims from Bike Friday could be many more weeks apparently. Glad I'm not stuck somewhere. Ben at Venture Bikes has built me some nice wheels for best bikes but Mavic non longer do wear indicators apparently. One set are last year's and have a deep wear indicator. Just done rides around the block but they feel great.

I really wish people would not start this sort of discussion without thinking. Having checked my rims, the only winner is Paul Prince and the only looser is my bank balance.

The calipers arrived this morning and the rims on both wheels are down to about 1.1 mm at the thinnest points so there's a little life left in them, but not much. In a stroke of better luck, I found a pair of last year's model Mavic Ksyriums heavily discounted online.

This is a quite good idea to get a more accurate measure other than using a ball bearing like I do.

CakeStop wrote:Hmmm, just did a quick finger test on my 8000 mile old OPs. The rear feels OK but the front feels a bit thin, needs closer inspection I think. I'm sure I wore the rear one out first last time.

Closer inspection of the front this morning suggests there's a bit more life in it but maybe no more than 2000 miles. I then started worrying about the rear, how can I possibly wear the front out first? Looking sceptically at the perfectly flat rear rim I eventually remembered buying a new rear wheel last summer because my attempts to restore a sick hub to health were unsuccessful

I did a check on my everyday wheels over the weekend and my front rim is getting to the point that it needs to be checked after most wet/dirty rides now.

But here is the rather bizarre thing, the rim wear indicator is in pretty much perfect condition, however the rim has very badly worn either side of it? When you put a straight over the rim, it touches at each side and in the middle of the rim, but there is a 0.5mm dip either side of the wear indicator where it has worn down?

Both the brake blocks are and always have been correctly aligned and sit central against the rim, so no idea how or why that has happened. I have certainly never seen rim wear quite so uneven as this before?