FOAM TIRE REPLACEMENT HELP

[limestang]

I have a couple of road cars I am in the process of restoring. The tires have the usual cracking and are dried out. Can anyone provide instructions on replacing them:

1) How to remove foam tires and prep surface for new ones
2) Good source for vintage size foam replacement tires
3) How to install foam tires and type of glue
4) General guidance on truing and how much to remove

I apologize in advance if there is already a thread on this topic.

Thanks Limestang

[REMJ666]

Try soaking them in acetone...Take one that is junk and try that one first...I know first hand that some of the cheaper plastic wheels will dissolve in acetone...So be careful...You can try the oven method...I use that one for rubber wheels...Turn on to 400 degrees and in 15 to 20 mins the glue will totally dissolve...Warning here...It will stink your house up something fierce...Turn on the exhaust fan and open the windows...But it works...

[terry.sc]

1) Depends on what the old tyres are stuck on with, for older tyres soaking in lacquer thinner will soften the glue, modern tyres are cyanoed on so need acetone. Or just rip it off and clean up the wheel on a truer or lathe. The rim wants the outer surface to be sanded so it is rough, if it is smooth and shiny the glue has nothing to grab on to. An old school trick is to cover the wheel in vinyl tape before gluing, so when the tyre is worn out you put a knife through the tape and just peel the whole lot off in one.

2) Hard to find any these days, most come ready mounted and trued for racing. CRC still sell some 1/12th donuts and [img=http://www.rc4less.com/index.php?cPath=5&osCsid=55d17bdcb1d44ec51dd5fd65544afd95]rc4less[/img] sell some dirt oval donuts that will do for 1/10th, but apart from that I think Corally is the only place that still makes 1/12th and 1/10th donuts, and all the places I know stock those are in Europe.

3) There are three ways of gluing tyres on.
The traditional way is to use a rubber contact adhesive. You coat the inside of the tyre and the wheel with adhesive and leave to overnight to dry thoroughly. When dry you then dip them in lacquer thinner to soften the outer layer of glue so you can slide the tyre onto the wheel, you line the tyre up as square as possible and again put them aside to dry thoroughly.
The new way is to use foam safe cyanoacrylate. You must use foam safe glue as it doesn't make the foam hard when it soaks into it. Fit the tyre on the wheel and line it up. Peel the tyre back over itself, run a ring of glue around the wheel and roll the tyre back over the glue. A spray of activator on the outside will dry the glue and will start working its way inside. Flip the tyre over and repeat on the other side.
The third alternative is tyre tape, a thin double sided tape. Put tape around the wheel, slip on the tyre, then pull out the backing on the outside of the tape. Easiest to remove after use, just cut throught he foam and peel it all off in one piece. Tyre is stuck instantly, but like contact adhesive it useful to run a small bead of cyano around the outside rim to stop the edge of the tyre lifting off the wheel.

4) Easy option, use a tyre truer. You can get fully automatic ones that do a great job and save you a lot of hassle but they aren't cheap. If you have a metalworking lathe a sharp pointed bit in that will do a great job. If you don't have a truer then I have seen people use power drills in a drill clamp with an axle in the chuck and sandpaper glued to a piece of acrylic or plywood to give a flat sanding board. If you don't have that, a motor pod bolted down to a bench with the diff locked up will do the job. Have the tyre spinning with the top coming towards you, so all the tyre removed will go away from you. If the drill or motor pod is mounted above a bench you can rest the sanding board at the back on the bench and bring the front up to the tyre, this keeps the board flat to the tyre. when the tyre is flat round the corners off before removing it. For the second matching tyre, keep on checking the diameter as you go to get them as similar as possible.
As for how much to take off, that is down to you. Older cars ran better with reasonably big tyres, todays cars work best when the foam is taken down to only a few millimetres, even to the point of wearing through to the wheel in a handful of racers. If you aren't planning on racing then just true them to whatever looks best to you.

[limestang]

Thanks terry.sc, I greatly appreciate you taking the time to share your knowledge and insights. I have a 7x12 mini lathe, so am looking forward to giving it a try.

- Limestang

[romulus22]

As for foam donuts, I searched and called tons of places. Luckily I'm right down the street from Johns BSR racing tires. At first I was just going to give him measurements over the phone but he suggested I just come up to make it easier. He found some defect tires and charged me almost nothing. Super nice guy and its all done in house so if you are having trouble finding off the shelf he's an option. If you decide to go this route you'll need to call later in the day and ask for John. He comes in later than his employees and stays late and he's the one you'll need to talk to.

http://johnsbsrracing.com/foam-tires

[integra22t]

back when i did oval i made my own tire truer out of wood and an old axel and motor .. i installed a board with 80 grit paped with a hinge at paralell to the axel .. the sides i just used a sharp knife and sand paper to take the sharp edge off

by the time i needed to replace the tires where small so i just used the tire truer to shave off the old tire and install a new set

[terry.sc]

I have a 7x12 mini lathe, so am looking forward to giving it a try.

That makes life easier. Stick a left side hub in the chuck with an old wheel and tyre on it, and skim the old tyre straight off.

For truing, the best way is to make a dedicated cutting bit, out of a piece of hacksaw blade. You need a way of holding it at an angle so the blade can cut the tyre as it works its way along the blade. Here is an example using a piece of brass hex, slotted to hold the blade.


Use a piece of sandpaper stuck on a strip of wood to round off the corners after you have trued the tyre before taking it off the lathe.

[THUNDERSTRIKE1]

Soakm with wd40 foams come off.Then wash and scrub with soap and water then scuff and reglue new foams in place.don

[cobalta70]

For truing, the best way is to make a dedicated cutting bit, out of a piece of hacksaw blade. You need a way of holding it at an angle so the blade can cut the tyre as it works its way along the blade. Here is an example using a piece of brass hex, slotted to hold the blade.

It looks like someone has a Taig micro lathe. Thanks for posting the picture. I have been thinking of making a dedicated setup for mine, but was not sure how to go about...

[Justin33]

I just did my first set of foams in over 15 years and i used tamiya tire tape instead of old school rubber cement and it made life so much easier i'm no longer scared to mount foams any more its great wish i knew about tire tape many years ago!!

[RC10th]

This sort of pertains to the original post.

What's the best way to glue undersized foams onto 1/12 rims? I've glued tires in the past but am affraid with this set as the rims (and 1/12 donuts now) are hard to come by. Some sort of tire horn is what I'm thinking. Only the fronts are the problem and you only really get 1 shot at getting the tire on properly.

The method I usually use is to coat the rim and inside of the tire in contact cement and let dry till the tack is almost gone. I then wet my finger in turpentine and rub the outside of rim and inside of tire and quickly slip them together on a flat surface, let dry and true.

Since this is a shelfer I was thinking of just truing the tire without gluing them which makes it possible to easily change the donuts later without marking the rims.

Opinions from more experienced tire gluers? Tire tape?