I had a new front tire installed a while back.  It had a slow leak (like, it'd be within reasonable pressure for a week or so), so I took it back and the shop supposedly fixed it.  It didn't take:



Our local shop (Big Twin in Boise) sadly CLOSED recently.  I'd gather the tire needs to come off and the rim needs some serious attention with an emery board or something like that (especially that second side, yeesh!).   Is this something I can tackle or should I try and find a local shop to fix it?

Caveat:  I've done all manner of deep engine work on my bikes, but for some reason I really hate working on tires! 

I would remove the tire from the rim and have a good look at it and the rim. If the rim is at all clean I would assume the tire is faulty.
If the rim is dirty you will want to use something like brake part cleaner to remove any rubber or bead sealer residue. Inspect the rim for scratches or other mechanical damage.
if the is damage I would use fine emery cloth to remove them and then buff smooth.

With the large amount of leaks you have I suspect there is a bit of the old tire bead stuck to the rim. The shop that mounted it should fix it in my mind. If they are reluctant or can't fix it I would find some else or do the work myself. Tires are to important to have to worry about breaking a bead while all banked up in a corner.

Based on the usual propensity for K100 wheels to leak as they get older, this isn't a job you can do yourself. You can do all the mechanical work (check the rims, dress out any obvious dings etc.) but at the end of the day, the rim has to be sealed with a rim sealant before the tyre goes on. Even then, it will only slow down the leak rate. Without rim sealant, Low Flying Brick drops 4psi per week in the rear wheel. With rim sealant, that drops to about 3psi every three weeks. The front wheel isn't as bad.

I had a similar problem cause by grit / grot between the tire and rim (both on my K100 and my car - second hand wheels and tires). 

There was really nothing I could do except get it to the shop and ask for extra sealer. All good since.

Good luck

Dai wrote:Based on the usual propensity for K100 wheels to leak as they get older,

I guess I have been lucky with never have much trouble with this once a tire has been proper installed.
Are some of the rims that porous or where is the air going? A good coat wheel varnish should stop it?

Being zaubertuba's photos show so much bead leakage I can't see how it is not some mechanical issue with the tire or the rim. Also he mentions that it started after a tire change which would lead me to look at that process. In my mind the tire needs to come off to properly assess the seal of the bead.

Dai do you really find that sort of bead leakage often on older wheels? Are particular wheels worse then others?

I do know a day of spirited riding can cause some air loss in new or old wheels.

A good reminder for all of us to check tire pressures often.

Zaubertuba, was this tire mounted by the firm that bought out BigTwin?

brickrider2 wrote:Zaubertuba, was this tire mounted by the firm that bought out BigTwin?

Actually this was installed right before they closed. Unfortunately life's been busy so the bike's been garaged most of that time. 

Sooo....somebody bought them out?  I'm in Nampa and don't get out that way much but last time I drove by the building was empty.

After Fred retired the BMW franchise passed to Dennis Dillon.  Some Big Twin employees moved to the new company, some chose to pursue other options.

gorio wrote:Dai do you really find that sort of bead leakage often on older wheels? Are particular wheels worse then others?

It's a known K100 problem. I think it might be mostly restricted to the earlier snowflake wheels, but someone needs to confirm/correct me on that.

My Y spokes definitely lose pressure at around 2 PSI a week. The 16v three spoke rear I have is much better, hardly ever changes.

I've never found the wheels on my 1995 K1100LT to leak air.  Actually, I don't recall that the 1985 K100RS had a problem in that regard either.  Maybe it's the luck of the draw.

I never had a problem with holding pressure in the snowflake or the three spoke wheels on the five bricks that came my way.  That is, until I had a $650 Metzler Marathon front/rear tire change at a shop outside of Denver on my K75RT three spoke wheels. 

Both tires lose 15# per week until they get to 10-12psi.  The Shinko's they replaced could go months with no loss of air. 

I need to take the tires off and clean the rims.  I think I need to double check the balance of the wheel as well.  Both wheels, especially the front, have what appears to me to be a massive number of wheel weights.

And people I know wonder why I insist on doing all my own work...

You need to find out where it's leaking. Either fully submerge the wheel in water the preferred method, or use a spray bottle filled with soapy water. Due to not being able to find a place to get my rear wheel balanced on Brisbane north side I built a static balancer. Mk 1 version was a blade type and while it did work it was over sensitive and time consuming. Mk 2 version was four bearing type, mounts to two saw horses.
Regards Martin.

I've owned or used many K's (maybe 30), much more Airheads with the same front-wheel and only had one single problem of air leak on a 85 K100.
I simply had to clean, with a metal brush, the inner bed of the rim to solve it.
Actually, I do it at every tyre change (I do it myself), to remove gum or mounting grease sticking on the ream.

Note that the BMW genuine metal valve uses a O ring, that may be leaking with years.
I seldom noticed leaks with defect standard valves.

Sorry I forgot to report back!

So I managed to pull the tire, cleaned up the rim with a brass brush, then solvent, then (lightly) sanded with 400-grit paper.

Our local O'Reilley's happened to have bead sealer.  I got some and used it. 

Refilled and balanced. Martin I love your balancer but I didn't have any bearings so my "ghetto" balancer looked like this:



You just need to wiggle the axle back and forth in small increments to break the surface tension of the bearing grease. Takes some patience but it actually worked well!

Aaaaaand...the results are:  3 weeks out, only 3 psi down.  I can live with that!  

Your balancer is similar to the MK1 version except I used aluminium angle. The bearings are over 25 years old, they are stub axle bearings left over from Go Kart racing days. I knew I'd find a use for them.
Regards Martin.