Bottom Bracket and Dura Ace Crankset Questions

Two questions really. First, I’m building up a Cervelo P3 frame. I assume the threads are English and a standard 109.5 bb will work for a double chainring setup? Anyone??

Second, there are a couple models of the dura ace double crankset. Is there any difference between the 7700 and the 7701. Shimano’s website lists the 7700 as the triathlon model. Is that just because of the chainrings it comes with. I am planning on running 42/55. Can I use either model.

Thanks. I’m sure there will be more as I progress.

sweet

Two things: The 7701 model is the TT/Triathlon model. And, though you didn’t mention it, I would suggest putting the Ultegra BB in, vice the DA. The DA is nice, but unless you have a lot of money to keep paying your LBS to adjust it every 2-300 miles or have a dedicated mechanic like the pros, you’re better off with the Ultegra. Its pretty bombproof and you’ll only need to check it when you do major drivetrain serviceing every 1000-1500 miles. Even then it’ll most likely be fine.

TriBriGuy is right! Ultegra is absolutely the bb to put in. I have one each da and ultegra and I wish that they were both Ultegra.

Get the Dura Ace BB. I’m not certain which DA BB the following posts are refering to. Maybe from a few yeers ago, but a sealed DA BB is available. Shimano finally got their head on straight!

Also, the DA TT ring is the solid ring. I’ve got a 56-44 and have ridden on both chain rings. There isn’t much difference between the two though the solid ring may be a bit stiffer. You’ll feel it when you pedal.

My 2Cents

The Dura-Ace bottom bracket is excellent but you do have to install it correctly and follow the instructions for installation carefully. From our experience the customers who have had issue with Dura-Ace bb’s are the ones who have had a less than meticulous installation done by someone. You actually do benefit from reading and following the little instruction sheet that comes with the components!

I double-checked the shimano website and they list the 7700 as the tri-specific crank. Let me re-phrase my crankset question. If I am just buying crankarms, will either the 7700 or the 7701 crankarms be compatible with big chainring combos (either 42/55 or 44/56)?

The bottom bracket debate is interesting as well. Were you Ultegra fans referring to the old dura ace bbs or the current models?

Thanks again.

sweet

These are all the same bolt pattern.Chainrings are interchangeable.

If I am just buying crankarms, will either the 7700 or the 7701 crankarms be compatible with big chainring combos (either 42/55 or 44/56)?
The only difference is the chainrings the 2 models come with, the 7700-Triathlon comes with the big, solid rings, the 7701 is the std road model. Bolt circle diameter is the same on all Shimano road cranks.

Quote - Were you Ultegra fans referring to the old dura ace bbs or the current models?

The old 7400 series Dura Ace BB was great. The 7700 series is crap. I think the design is OK, but the materials used are too soft and damage easily. Ultegra BB is the way to go.

Exactly the info I was looking for.

Thanks

Sweet

I spoke with a Shimano rep at the Endurosport open house in November and he recommended going with the Ultegra BB and duraace cranks as the best combination for serviceability.

I’ll append my previous post: Unless you have a dedicated mech like the pros OR have Tom or someone similarly scrupulous in servicing bikes, stay with the Ultegra. No offense to “a lot of bike shops” but so many employ second rate or inexperienced mechs and don’t properly supervise the jobs. Save yourself the hassle and put the Ultegra in. All but the most apelike buffoons can get it properly installed. You’ll spend more time RIDING your bike.

The 7700 and 7701 cranks are not the same, the 7700 were the first incarnation, the 7701 the more recent 9 speed offering, they have nothing to do with the chainring size offered on the cranks. As Cullen points out, any 130mm BCD chainring will mount on them.

7700 Dura Ace cranks are forged solid, machined from the backside, then a cap is welded on and remachined smooth. This capped construction is how the crank is made hollow.

7701 cranks are forged with a void or air pocket in the cranks and do not need the expensive and meticulous rewelding of the cranks. They won’t have the “OK” sticker that verifies the integrity of the weld because they are not made that way. They are also about 21 grams lighter for a 175mm size, but that mass can actually vary from crankset to crankset and from size to size.

-SD

SuperDave has it spot on. Get the 7701 set! And the others are also making a point re: the BB! I have the 7701 group on my road bike. Complete DA groupset BUT I use the Ultegra BB. This isssue has also been debated and confirmed 1000’s of times on roadbikereview.com forum. The latest 9 spd DA BB has got issues (unless you are prepared to maintain it every 500 miles).
Hey, Why not go for the new 10spd? The new 10spd DA is AWESOME!!! I built my P3 with it, the new BB chainset combo is SO easy to install… I cannot say enough good things about the new DA!

According to the Shimano Europe site, both the current road and current tri cranks are the 7701 series.

As for the bottom bracket, I would go with the Ultegra. While Dura-Ace is now supposedly better sealed, it also has soft aluminum cups that are prone to boogering. This is where some of the weight savings come from. Personally I’d rather pay the miniscule weight penalty.

But as another poster said, if you’ve got the coin it’s hard to beat the new 10 speed crank system