Monday, August 15, 2011

Gluing up some new tires on some old wheels

I developed a technique that I describe here that I think is a great way to remove old glue from an aluminum rim.

This week, I glued a new pair of Challenge Grifo Cyclocross tires onto a set of Mavic Ksyrium SL aluminum wheels.  The first step, of course, was to stretch the tires onto a old set of rims. I then pumped up the tires to about 60 psi and let those sit for several days. I also add some sealant to the sidewalls while the tires are stretching and the sidewalls are still nice and clean. I then went about removing the old Grifos from the wheels. The front tire came off with the usual amount of prying and tugging. The rear tire took a bit more effort and I had to use a bicycle tire lever to pry up the tire. I then I slid the lever under the tire, between the tire and the rim to further work the tire off and use the leverage of the tire iron to get the tire off. It eventually came off.
I was now faced with an ugly view of old glue on the rim and I needed to find the best method of cleaning the old rim, prior to gluing the new tires.

I had seen and read about several methods of removing glue online. One method involved heating the rim, a section at a time with a hair dryer to loosen the glue, and then pick off the glue with a dull butter knife. That method proved to be rather inefficient. Here is a picture of a small section of the rim after heating and picking glue off.
This effort took me 15 to 20 minutes to complete.  For 20 more sections on my Ksyrium, it would conservatively work out to be 300 minutes or 5 hours of work per wheel. 10 hours of painstaking heating and picking for two wheels. Not to mention the many Band-Aids for all the nicks and cuts on my fingers and hands.
Others recommend scraping just the big chunks off and then coating the rim with some fresh glue. The idea being that the new glue will fill in the voids and irregularities of any old glue still on the rim. Many blog entries say that its never necessary to remove all the old glue. Others recommend removing all the glue with chemicals, such as acetone.  The problem in my mind with using chemicals is the risk of any chemical residue left over from the cleaning will compromise the new glue that needs to be applied. Besides, Acetone is really toxic, so I was not going to use acetone.
I remember seeing some pictures online where someone used a grinder of some sort to grind off all the glue. That gave me the idea to use a portable electric hand drill with a wire brush to remove the old glue. Here is what I did. I used a wire brush as pictured here:
Remember, I am working on aluminum rims. NOT CARBON! With the wheel positioned on a piece of wood on the floor, and one half of the rim held between my knees, I used an electric drill with the above brush attached, to scrape off the glue. The outside edge of the brush fit nicely into the curvature of the rim. I also found I could regulate the pressure applied and get nearly all the glue off the small section of rim in seconds. The result looks like:
I cleaned the entire wheel in about 5 to 10 minutes. What I also discovered was, with the brush spinning at such a high rpm, it would simultaneously heat, soften, and remove the glue. Depending on how long i kept the brush moving on the rim surface, I could actually leave a very thin layer of glue on the rim. The rim surface looks clean but there remains a very thin layer of glue. I am thinking that this will be a good thing. I would think that if there is any dirt on the rim, the dirt would absolutely have to come off. In my case, the rim was not contaminated with dirt; it just had a lot of chunks of old glue.  I was  careful not to grind down to bare metal. As you can see from the picture, the original paint from the rim remains. What is not apparent from the picture is the surface is very smooth to the touch and ready for a couple of thin new coats of glue.
I would like to hear people’s opinion on this method. Are there any flaws in what I have described here that I am not aware of? What do folks think of this method of cleaning old glue off of rims in preparation of gluing on new tires?


dkrice said...

Such attention to detail, Dave! If nothing else, the wire brush has roughened the rim enough (similar to sandpaper on a tire tube) to give the glue better purchase. On old rims I usually leave most of the old glue inplace, figuring the rough surface will adhere better. Your result has to be better than my recent effort. Brand new Neuvation tubulars with Grifos, mounted with three coats of glue about six weeks ago. I took them out of the basement this weekend in prep for Blunt Park, and I could easily peel the tires off the rims! They were rock solid six weeks ago! So, 2 more coats of glue later, I am hoping they'll stick!

Dave Beals said...

DKRice, This is what concerns me. I know you to be a capable and competent bike mechanic, you followed all the right steps (apparently, you did right?) and yet you could easily peel the tires off the rim! Yikes. The only thing i can think of is because you used new wheels, did you prepare the rims, rough them up a bit? and did you do 2 more coats? like one on the rim and one on the tire?

dkrice said...

Dave, I think my mistake was not roughening up the new rims. By the looks of it, YOU will be fine!

Dave Beals said...

Oh, and here is an important (if belated) safety tip if anyone might be thinking of using this method: wear safety glasses.