Wednesday, December 1, 2010

Q&A: Fixing Dented Deep-Dish Carbon Wheel & Lacing Spokes

Winter's a great time to get your equipment ready for next season and to work on your mechanical skills, like wheelbuilding. From this week's mailbag, here are two related Q and As with feedback and photos from the cyclists showing their handiwork.

This first question is from my Bicycle Trip/Symantec teammate Miles, who is one of our top 45+ masters racers.

Dented carbon rim
Q: Hope you can help me out, Jim. I wanted to make my race bike even faster with some deep-dish carbon sew-up (tubular) wheels. I did my research and decided to buy some made by Edge, which have a great reputation (FYI, they changed their name to Enve recently).

These are pricey wheels so I decided to search eBay and I found what looked to be the perfect pair at a sweet price.

I won the auction, but when the wheels arrived I was depressed to find a large dent in the front rim. Here's a photo. Did I get ripped off? Should I send the wheels back? They're very true and round and all the spokes are nice and tight. I can't see any other signs of damage but I hate this dent. What would you do?

Thanks!
Miles

A: You said the wheel is very true and round and all the spokes are nice and tight. That's good, Miles. As long as there's no other damage (did you check for cracks in the rim where the spokes enter it?) - the dent is probably only cosmetic damage not unlike when a shopping cart rolls into and dents your car. It's ugly and frustrating, but it won't affect the strength of the wheel.

Tall, deep-dish carbon rims like this are often pretty flimsy. You can squeeze them and make the sidewalls flex a lot so it's easy to see how someone running into the wheels in the race pack could have done this. Or maybe, just putting them in the back of a car and someone putting something on top of the wheel dented it. So, it pays to watch out for stuff like this.

Why don't you bring the wheel over to my home workshop and I'll check it out and see if it's fixable? I'm thinking we can pop it out similar to how you'd get a dent out of a car fender.
Dent removed with a little prying and heat
Miles brought the wheel over and I confirmed that there was no structural damage and that it was nice and true and round - a good reliable wheel with a dent in it. Miles wanted to try to fix the dent himself so I told him to:

Take a smooth tool like a regular screwdriver and put it through the hole in the rim right at the dent and using the tool, gently put pressure beneath to push out the dent until the surface of the rim is flat again.

I told him to have his daughter hold a hair dryer and slightly warm the rim at the dent at the same time he was pushing the dent flat. This procedure worked perfectly as you can see from the photo Miles sent me.

Nicely done Miles! Enjoy your speedy new wheels and I'll see you at the San Bruno Hillclimb next month. Jim
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Q: Hi Jim,
I'm a bike tech at REI part-time, as well as a DIY working on my motorbikes, and of course, a cyclist/racer.

I'm building a couple of wheels, and it would be great if I had a jig to hold the hub upright while I'm lacing the spokes. Do you know of any simple jigs that are made for this purpose? The jig should be able to adapt to a wheel with a solid or quick-release axle.

Thanks,
Ronyd

A: You might need to explain a little more in order for me to think about it and see if I can think of a jig that would help you out, Ronyd. Because the way I build wheels doesn’t require a jig until I start truing and tensioning.

I fan the spokes and drop them in
To place the spokes in the hub, I hold the hub in my hand so that I can use gravity and let the spokes drop into the spoke holes. I put the first set of 8 or 9 spokes in one side of the hub. Then I place the first spoke in the rim and attach a nipple.

Next I hold the rim and lace the other spokes in that batch to the rim. This partially built wheel becomes the jig and I drop each set of spokes in and lace them up until all the spokes are in the wheel.

This is a super-fast way to lace up a wheel and you’re always holding the hub or the wheel so you have an easy time controlling things. I don’t know if you saw this page on my website, but it has photos that should give you an idea of the wheelbuilding process I follow.

I’m not saying you have to build a wheel the way I do. I’m just explaining why I don’t have a jig idea for you. Maybe if you describe your technique I can think of a jig that might work for you.

I did work with a mechanic once who wanted to drill a hole in his workbench so that he could put the hub’s axle in it to stand up the hub because he liked to place all 36 or 32 spokes in the hub first and then lace up the wheel once all the spokes were in the hub. That’s the way the Schwinn bike mechanics school taught mechanics to build wheels, but I always found it confusing for people.

But maybe a simple piece of wood with a hole in it for the axle would work for you? The wood could be C-clamped to a workbench so you could put it wherever you need it.


Jim

Ronyd's wheel-lacing jig
Ronyd replied:
Jim - Looks like you hit it on the head in your last paragraph. I too, was taught to drop in all the spokes, and then start lacing, drive side first.

A couple of things I noticed: first, is now you have too many spokes hanging. Secondly, I found myself bending the spokes over to the correct position before I could actually do the crossover.

So, I decided to either go with Barnette's technique, doing 4 groups, flipping the rim over for each group. Or, try your method. Either way, sounds like it's freehand.

I'll experiment and see what work best for me. Thanks for the advice. In the meantime, I built this simple jig this morning for a few bucks out of plumbing pipe and flanges and it's doing the trick.
Ronyd

Thanks for the photo, Ronyd. Your jig looks perfect! Have fun building those wheels.
Jim

2 comments:

Lee Springett said...

Hi Jim,

Know this was a long long time ago. I have a set of wheels in a similar situation. Was just curious. When you say about putting a small flathead through whole in wheel by the dent I gather this means undoing he spoke to get to the hole then putting back it.

If this was the case will the wheel need truing again after?

My front wheel has quite a few dent but the spokes to looking to repair.

Thanks
Lee

Jim Langley said...

Hi Lee, Actually, you don't have to undo the spoke. You remove the tire, tube and rim strip and then you will have access to the top of the spoke/nipple hole. On deep dish wheels, you can put a flat object like a screwdriver in there through the hole to push against the inside of the rim. The spoke nipple is actually down at the apex of the V profile of the rim. So you don't have to remove it. Depending on what damaged the rim, you might need to true the wheel, but you won't need to remove a spoke and completely retension that spoke. I hope that helps,

Happy wheel repairing,
Jim Langley