Time Trial / Time Trialling / TT

I'm a couple of kilos lighter but I'm not sure that makes up for the 300W shortfall...

TT obvs.

did the course in the opposite direction, its fast and the reverse version avoids the massive* climb over the junction so its a little faster...

*its not massive

Maybe, what's the sizing like compared to Bonts/DMTs do you know?

Probably about same as bont. I used to use 46 bonts.
But don't hold me to that.

Ta.

I'm riding the FUCT fixed 10 at the end of the month and I'm motivated to do as good a time as I can. However I've made some positional changes to my geared bike that are impossible to replicate on my track bike and result in me being 60-90seconds slower on the same course on fixed. So, since it's my last tt of the season I'm thinking I might strip the derailleurs off my p2 and run that fixed.

This would involve
1) keeping the road axle on my disc (zipp900) but flipping it over to use the fixed thread on the other side. That means I would need to use a conventional QR skewer, and would leave the freehub body exposed on the NDS. Will this setup kill me, and will the chainline be alright? I know @xavierdisley has experience running cervelo tt frames fixed, but I think he uses a respaced track axle.

2) It would be convenient to keep my current cranks and chainring (my track cranks are a different length, bcd and bb). Is there any problem running a regular 10sp chainring (with ramps and pins) with a 1/8 track chain? Obviously I won't be changing gears so so long as I tension the chain properly it should be OK right?

3) dropout length is a bit short but should be OK if I set the chain length appropriately?

Is this going to work, or should I just take the track bike?

I'd run the Zipp flipped round with a 3/32 sprocket and chain with the chainring on the inner position. Definitely use a chaintug.

That picture is a 120mm Powertap track hub just with 2x5mm spacers. If you can find some spacers it's a piece of cake to use the Zipp and the track axle, if you want to run QR then yes chaintug for sure

I'm on 46 Bonts, how much are you after? Trying to work out what shoes to use with the Brim Brothers cleats in a few weeks!

Yep, I've ran a Zipp 900 as fixed, just used a chain tug and a good quality (not lightweight) skewer. Pretty certain it gives a spot on 42mm chain line.

edit didn't see the bit about running it on a road frame. As @umop3pisdn says run it on the inner ring. I've never owned a track crankset, I've always used road cranks set up on the inside.

Yeah a track conversion axle would solve everything, but they no longer make the ones for the 182 hub and they are like hens teeth 2nd hand. Magicman from TTF has one that I've dibsed but he needs to buy a new track disc before he sells.

If I use the QR (shimano closed cam), will the little bolts in the dropouts not be sufficient to keep the wheel in place?

will the little bolts in the dropouts not be sufficient to keep the wheel in place?

Yes, they will be fine in place of a tug. And the chain line is what it is, changing the axle doesn't affect it as long as the rim remains in the middle 😀

Perfect, so all I need is a new 3/32 sprocket and chain.

How much time will removing the rear ultegra brake gain me? I only need 10 seconds to beat last year's winner :-)

It's been faultless all season, until now: I can't believe it's a "system" problem, but something that's developed and which I can't identify.

Or co-incidence, in which I also have no faith.

PS How's your cock?

Ultegra? About eight seconds.

Could you remove a 105?

That would be closer to ten.

If Xav isn't, I am.

Dry fit looks promising. Needed to add a 2.5mm spacer on the driveside of the bb to stop the chainring bolts fouling the frame, and to my eye it also improved the chainline fractionally. Obviously need to remove the rd and rear brake but I'll have a test spin on Sunday.

Also I will need a chaintug as i can't fit the chain when the little screws are properly extended.

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Needed to add a 2.5mm spacer on the driveside of the bb

How does that work? Looks like a GXP crank, the chainline is controlled by the NDS bearing location.

I will need a chaintug as i can't fit the chain when the little screws are properly extended

Dial in the axle position with the adjusting screws and use the master link to join the chain after wrapping it around the chainring and sprocket :)

How does that work? Looks like a GXP crank, the chainline is controlled by the NDS bearing location.

Err... it is gxp... did I do a bad thing?

The chainring is mounted on the inside position and the bolts were rubbing on the chainstay so I wanted to move the driveside cranks outboard a fraction. I just found a random spacer in my toolbox, took the driveside bearing out and popped the spacer in before reassembling.

In the picture I added the spacer where I have drawn the green ring... is this wrong?

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is this wrong?

Yes, because the NDS bearing is supposed to be captured between the shoulder on the axle and the NDS crank. If you add the spacer, the NDS crank will try to pull the DS crank through the DS bearing, because the shoulder won't have reached the NDS bearing to stop it. Either the BB will bind up because the DS crank is hitting the DS cup, or if you loosen the NDS crank bolt to relieve the binding, the NDS crank won't be far enough onto the spline and it will be damaged by pedalling torque.

Humph... so is it possible to space the DS crank outwards?

The chainring is currently mounted on the inner position... I could potentially avoid the chainring bolts hitting the chinstay by mounting the chainring backwards, meaning that the bolts sit inside the little countersunk recesses on the front of the chainring, rather than the flat surfaces on the rear, however presumably this is also not a good idea?

Probably best to just use the outer chainring position and accept that the chain-line will be very slightly out (via my eyeballing method)?

so is it possible to space the DS crank outwards?

On a GXP crank, the only legitimate way to move the crank to the right is to cut material off the left side of the BB shell.

Flipping the chainring over is OK, you'll just use the other flank of the teeth which hasn't been worn yet.

Cool, thank you. I'll try on Sunday... Audax tomorrow.