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Ask Nick: replicating postition from bike-to-bike; swapping chains, cassettes between SRAM and Shimano

  • By Nick Legan
  • Published May. 17, 2012
  • Updated May. 17, 2012 at 3:05 PM EDT
Photo: Nick Legan

Q.Nick,
As a pro mechanic, I’m sure it was essential to measure and record rider data in order to reproduce perfect fit on new bike builds or upon reassembly after travel. In your opinion, what are the essential measurements needed to assure reproducing bike set up, and how do you measure (from what point to what point) in order to maintain consistency from bike to bike.
– Matt

A. Matt,
It’s becoming easier and easier to replicate positions these days. Many teams now carry around custom-made position jigs or a Retul system to check everything very precisely.

Replicating a position with a tape measure and a steady hand is a little trickier. But a little forethought and practice can lead to extremely accurate work. I used a four-foot level and a drywall square to help me with measurements. With them, I didn’t need to find level ground, simply a fairly flat surface. The level was used more as a long straightedge to average the ground between the two wheels.

I used the drywall square, in conjunction with the level, to have a perpendicular to the ground (or averaged ground established by the level). With the level on the ground, the drywall square slides nicely along the top of the level.

I always make sure to use the same tape measure. Accurate measurements are all about repeatability. It’s tough on the road because every parking lot is different. For you, at home, it’s actually a bit easier.

Have a space where you always do your bike measurements. Mark where your tires hit the floor and then always perform your measurements in the same place. That will help a lot.

On to the measurements. I perform these measurements, in this order, to set up a bike.

1. Saddle height is obviously important. And there are a million ways to measure it. Personally I measure the length of the saddle and mark the mid-point along the top of the saddle with a Sharpie. From that mark I then measure to the center of the bottom bracket. Always note crank length and pedal choice. These have obvious input into actual leg extension.

2. For saddle setback, I use my perpendicular setup described earlier. With the level on the ground and the drywall square sliding along the top of the level, I set the front edge of the drywall square at the front of the saddle nose. Then I measure forward to the bottom bracket.

3. Drop from the handlebar can be measured using the level (but that assumes a level ground, though it doesn’t matter if you always measure in exactly the same spot) or by measuring from the top of the saddle to the floor, measuring from the top of your bar to the floor and then subtracting to find the difference.

4. Reach to the handlebar can be done in an X/Y method, or simply by measuring from the tip of your saddle to the center of the handlebar.

Those four measurements are a good start when it comes to setting up a bike. There are other measurements that can help when installing handlebars, etc. It’s vital to practice and think about what you’re actually measuring. The most important thing is to set up the saddle first and go from there.

Q.Nick,
I have a 2010 BMC Promachine. The seat clamp area on the frame has two bolts that require different torque settings. Around the lower bolt it appears that the clear coat has chipped off, not sure why. Should I cover that with something or is it okay to leave the bare carbon as is?

I noticed it when adjusting my seat post height, I always use a torque wrench when setting those bolts. Any insight would be helpful.
— Marco Camuzzi

A. Marco,
As long as it’s only clear coat that’s coming off, you’re okay. If carbon strands are broken, you should take it to a BMC dealer. Remove the bolt completely and give the area a good inspection. My bet is that you’re just fine, but it’s always better to scrutinize the area than it is to just keep riding it.

Q.Nick,
I’ve been riding a SRAM Force cassette with a Dura-Ace chain for a few years now because I find it to be cheaper and smoother than SRAM chains. However, I heard that the new 2012 SRAM chains — PC1091 and above — are a real improvement over previous models.

Competitive Cyclist claims, “the icing on the cake is that the PC-1091R is quieter this year than the 1090R due to more heavily chamfered inside edges on the outer link plates.”

What’s your opinion? Is it worth the purchase? And, what’s your view on the compatibility of SRAM and Shimano chains and cassettes? It appears to be one way, with most agreeing that a Shimano cassette with a SRAM chain is fine, but a SRAM cassette with a Shimano chain — my setup — is not.
– Neil

A. Neil,
Neither Shimano nor SRAM will want to hear this, but I routinely run Shimano and SRAM cassettes and groups interchangeably. I pay little attention to it to be honest. They all shift extremely well.

SRAM’s new chains do seem to shift better. I would agree with Competitive Cyclist’s comment. I’ve run both the setups you describe without any troubles. In the past, SRAM teams used Shimano chains and they worked great, but now SRAM teams run full SRAM.

All this said, I do feel that the ideal setup is using everything from the same manufacturer. That isn’t just marketing. They are designed as systems. With the introduction of SRAM’s new Red group (with ideas sure to trickle down to Force and Rival), Shimano, SRAM and Campagnolo all produce incredible shifting. Before, I would have argued that Shimano had the best front shifting and SRAM matched Shimano and Campagnolo with its rear shifting. The new Red though has taken SRAM’s front shifting to another level. It’s so smooth, it’s eerie.

I think greater differences are felt due to the mechanic that works on a given group. Those that are particularly adept at Campy have tricks to keep them running so smoothly. The same goes for Shimano and SRAM. I’m not one to pick favorites, but from a mechanic’s perspective (mine), Shimano makes it easiest to set up a perfectly functioning bike. Campagnolo and SRAM require a bit more work.

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Nick Legan

Nick Legan

After graduating from Indiana University with honors and a degree in French and journalism, Nick Legan jumped straight into wrenching at Pro Peloton bike shop in Boulder for a few years. Then, he began a seven-year stint in the professional ranks, most recently serving for RadioShack at the Tour de France and the Amgen Tour of California. He also worked for Garmin-Slipstream, CSC, Toyota-United, Health Net and Ofoto. Legan served as the VeloNews tech editor 2010-2012 before sliding across the line into public relations.

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