Sunday, February 15, 2009

Equipment - SRM Updates

I first wrote "Upgrades" in the title but I think "Updates" is more accurate. I'm not improving anything per se, just refining fit and function. I had two major missions in mind back in late 2008, both gelling when I rode my trainer.

First mission: fix my broken SRM mount. My standard mount sits on the downtube just inside of the chainring spider. I broke the mount in a difficult moment on a ride (I was way anaerobic and had to shift down), and my oxygen-starved brain didn't shut off my legs until I'd sort of trashed the mount. An extra zip-tie and some electrical tape and I made it through the season, but I wanted to fix that for 2009. Also, if I was going to replace this thing, I wanted it to register speed on the trainer, so I wanted a rear wheel speed pickup.

Second mission: get 175 mm crank arms. I rode my 175 equiped Giant and felt like I could turn over gears with ease. When I got back on the 170s they seemed hard to push, like the bearings were binding. I decided I wanted 175s once again.

The first thing was to buy and install a bottom bracket sensor mount. I ordered this just before I left for CA, and in the "Notes" part of the online order form I requested that they contact me if the part would (at my house) arrive after Tuesday Feb 10th. I wouldn't be there on Wednesday (I'd be on my way to California) so I figured I'd give them the CA address if necessary. To my surprise I got a very nice email from the folks at SRM saying that I'd have the mount in plenty of time, and on Friday (?) it showed up. It came USPS (i.e. US Mail) so it may have been Saturday. Either way I decided not to install it in the flurry of "get ready to go" tasks. I just stuck it in my bag to take out to California.

The second thing on my list was to buy and install 175 mm crankarms on the bike. I've gone on and on about long cranks and, well, after riding shorter cranks for a year, I'm convinced that longer cranks suit my riding style better. 5 millimeters - it seems like a minor thing, I know, but those few millimeters give me an incredible feeling of power when attacking short rollers and such. I also think they work well for me when I'm not in great shape, and, honestly, I think I fall in that category right now. And when I say "not in great shape" that's relative to me, someone that isn't in great shape in general.

The tricky part with the uber-cool Cannondale SI SRMs is that you can't buy the crankarms separately, at least not readily. (Readily = from SRM, as I've found them to be super-efficient, knowledgable, and friendly - my transaction above was my third pleasant experience with them). So I had to go and find some cranks on eBay, doing a Buy-It-Now to assure myself that I'd get the cranks. Since I couldn't find cranks in time, I had to do the BIN on Monday night, only a day and change before I left home. Obviously the cranks wouldn't make it to CT by the next day so I asked the seller to send them to the CA address.

And lookit what the postman brought to the house!

(btw don't open the big pictures for the three below - they're all blurry as I don't have my normal camera and I didn't borrow Rich's).

The new 175 is sitting on top of the 170s. "New" is relative - they're new to me. Note the slight length difference.
(And, yes, I know, my bike is absolutely disgustingly dirty.)

The 175 right arm, complete with non-SRM spider and two chainrings. Looks naked, the non-solid spider.

See that round notched thing (lock ring) in the center of the crank? That's what holds the spider (the 5 arms) onto the crankarm.

I learned a bunch of things while researching exactly what I needed to do.

1. The SRM Cannondales come with the tools necessary to remove the crank as well as to remove the spider from the crankarm. It even includes an extra spider, so if you really wanted to, you could "lighten" the bike just a touch by using the standard spider. I remembered this on Monday or Tuesday night (last minute packing) and put the tools in my bike bag. Phew.

2. For instructions on how to remove the crankarm, just go to Cannondale's site. They have good instructions on proper technique. Regardless of what they say, this is what I did - unscrew the soft aluminum bolt holding on the arm; screw in the "inner" steel removal tool; screw in the outer steel removal tool; unscrew the inner removal tool (the inner tool immediately hits the outer one and, if you keep unscrewing, it forces it out, along with the crankarm); hold arm and marvel at the intricate machining.

I italicize inner because I didn't do that and almost broke my cranks. My friend (two mechanics are better than one) watched me for a bit then said, "Hey, shouldn't you unscrew that piece instead? Because that's how normal crankarm removers work..."

Oh. Erm. Yep.

3. To remove spider get big removal tool, get 3/8" drive socket, and unscrew normally. This means unscrew in a lefty-loosey motion if you look at the spider from the back. The spider and arm come apart like magic.

Tool and lockring on spider. They fit together very precisely.

4. The SRM spider and standard spider are machined perfectly. They both fit immaculately. Beautiful.

Beautiful machining. Click on the picture for a big version. You can see the intricate machining in the center of the spiders, the matching bits on the crank arms (one with the pedal and the arm above that). The pin tool is visible, along with the crank arm removal tools (left is outer tool, right is inner tool). I have the spider lockrings sort of haphazardly piled towards the bottom.

5. To tighten spider, put arm and spider together (they're keyed so you can't rotate them), reinstall lockring carefully and tighten to proper specs.

6. To install crankarm, place on spindle and tighten crankarm bolt to proper specs.

(Note: my idea of proper specs cannot be published since I'd then be liable if anyone's cranks falls apart - always follow manufacturer's recommendations.)

Now my bike has 175s. Beautiful. I just gotta get better (at least not so sick I can't think straight) so I can ride.

On the way to installing the arms I also hacked my way around installing the rear wheel + BB sensor SRM mount. It's easier installing the sensor kit when the cranks are off, so in the middle of the crank thing I did the sensor thing.

1. I first taped the two wires together from the SRM head (PowerControl) side to the sensors. I prefer to have one thick wire than two little ones.

2. Then I put the BB sensor on. That's my base so I started there and radiated outward.

3. I ran my "two-wires-taped-together-as-one" (cue U2 here) along the downtube and up to the PowerControl.

4. I then ran the rear wheel pick-up as far back as I could. I don't have a magnet so I'll have to align things up later.


This called for a nice stiff drink. Or steak salad, garlic fries, and a short shopping trip to buy some orange juice and other training essentials.

My friend took my bike for a spin, so he's the first one to ride the bike with that combo. It was kind of hard to read the PowerControl, and we didn't zero it first, but he mentioned seeing 360 watts or something. Mind you he's riding a bike 13 cm smaller, in sneakers and pants. But, still, the number seems low, so I'll have to check that initial SRM number thing before I ride tomorrow.

I just realized I should do the ratty tape over, and swap the super heavy (and cut) tires out for the lighter and nicer Krylions, but if it doesn't happen, not critical. I can do it next week.

Hopefully I am good enough tomorrow to ride a bit. Legs are totally fine, no soreness anywhere (saddle, legs, arms, shoulders, neck).

I'm ready to train. I just hope my body is too.


Unknown said...

Great blog! A rare combination of quality writing and quality information.

I'm a new 35+ racer. I read that you switched to 175 cranks in 2003. What prompted that change? I ride a secondhand 54cm Cannondale that came with 175 cranks. I've since learned that 172.5 or even 170 is more typical for both that frame size and more generally for somebody my size (5'9", average limb proportions).

Aki said...

Thanks for the kind comment. The change came about because of the following ride.

Basically, for less than optimal fitness, I'm faster on longer cranks than shorter ones. I believe this is because I am a lower-rpm rider (under, say, 110 rpm ssteady), I struggle with steady power, and the long cranks are excellent for that.

I think that a very fit person can use shorter cranks (like I'd be on 170s) but even after many hours of training, I wasn't very good on 170s. So I decided to go back to 175s.