I have recently been cleaned out by an aging car and its various illnesses. I have $400 to spend on race wheels for IMWI this year. I have enough to get either a Renn Disc and go with my Kysrium SL up front or buy a CH Aero-cover and an aerodymanic front wheel off of e-bay.
So, again I will ask osome of those how many angels fit on the head of a pin technical questions.
Which option might conceivably be faster?
Would either set-up pose any technical questions, i.e. can an aero-cover fit on a Ksyrium SL rear wheel?
Would a Renn disc with a shallow front rim look too stupid?
find some one in your area that has a set of Spinegy Rev-X wheels for sale. i have a set and a Renn and the Rev-X/Renn is not a bunch faster then the Rev-X F/R. i would not buy a wheel set unless i could hold it in my hands! but i think that a set of Rev-X type wheels would be faster then a Ksyrium/Renn combo.
In terms of drag, I’m pretty sure the cover/ebay route will be
2) Would either set-up pose any technical questions, i.e. can an aero-cover fit on a Ksyrium SL rear wheel?
Is the Ksyrium a box rim or “semi-aero”? I got a cover onto a Bontrager race lite (22mm semi aero) but it doesn’t fit that perfectly. It’s much better to use a standard box rim.
3) Would a Renn disc with a shallow front rim look too stupid?
A disc is a disc is a disc so any aero cover is just as fast as the most expensive disc. Some people will talk about weight or stiffness but a few hundred grams will make no noticeable difference and unless you’re a 1000 watt producing indoor sprint track rider then stiffness is not an issue to be concerned about.
In terms of aerodynamics the cover with a decent front wheel will be faster than the disc with a less aero front. This is one of the set ups that I’ve used.
The CH Aero cover is designed for a box style rim. It’s important that the outer seal of the disc cover has a good fit with the rim or it will be less effecient. Some people will even run a bead of electrical tape around the outer circumference for this reason.
I remember a post by Andy Coggan when he talked about using one with a more aero dished rim for his power tap. He had to trim around the circumfrence of the cover to get a good fit, but it did work.
To me, this is a no brainer. Ger the cover and an aero front wheel. Renns are great. I own one. If you are looking for the more aero setup though, you have to take care of that front wheel too.
Which option might conceivably be faster?
Aero-cover and a front aero wheel
Would either set-up pose any technical questions, i.e. can an aero-cover fit on a Ksyrium SL rear wheel?
Ooo. Good question about using the Ksyrium and the cover. I’m not sure.
Would a Renn disc with a shallow front rim look too stupid?
Since the the front wheel is the one that breaks the wind first isn’t it reasonable to assume that if you are only buying one wheel the front wheel is much more important?.
That’s what I’d do. Apparently that’s what Steve Hed would do too. Actully I’m not really sure since the answer below is a mite flip-floppy. From the FAQ on hedcycling.com:
**Q. I can only afford one wheel, so which should it be? **
A. The front wheel breaks the wind first, so this is the most important of the two. In certain conditions, a front wheel will save twice as much as the rear. However, it also depends on the model of wheel, because a rear disc will provide at least as much performance as any other aero design on the front.
I agree with Pooks but will also add the only disadvantage of a more aero wheel in the front may be that you may notice more torque steer in windy conditions. You’ll notice it more if running something like a trispoke front and 32 spoke rear than if running a rear disc with the trispoke. Contrary to what some people believe, the disc/trispoke is usually easier to control than two trispokes. The IM Kona rule banning rear discs doesn’t make a lot of sense. Or at least the rule doesn’t have a lot of science behind it.
My recommendation if you’re on a budget - $59.95 CH Aero disc covers with either Hed Cx, Jet 60 or Campagnolo Shamal. Usually around $150. or so on ebay. You can also pick up a Specialized trispoke for around $250 or so. It is an earlier version of the Hed wheel.
You’ll be just as aero with this set up as the guy with who spent over a grand for new high end wheels.
Big Dave, a front rev-x off ebay might run you $150 plus a rear CHAERO cover is a very good setup plus you have $150 left to spend on other needed stuff. It is nice to know other triathletes are on a budget; if you see mismatched wheels, non color coordinated gear, $5 tinted safety glasses, and a 22 year old car at a race then you’ll know it’s me.
I had no idea that disk covers were so… acceptable. Cool! Maybe I WILL throw together a disk for TTs now after all. Do they make that same racket as the solid disks that routinely blow past me so quickly that they mess up my hair?
Would either set-up pose any technical questions, i.e. can an aero-cover fit on a Ksyrium SL rear wheel?
NO, an unmodified CH aero cover will not properly fit a Ksyrium. I tried this before and it is not workable with a stock cover. The only style wheel that works stock, is a box rim. Try open pro or MA40.
The CH Aero cover is designed for a box style rim. It’s important that the outer seal of the disc cover has a good fit with the rim or it will be less effecient. Some people will even run a bead of electrical tape around the outer circumference for this reason
They put a bead of tape onto the braking surface?
I like the idea of using my $60 cover over a $900 Zipp, but I do worry about a mechanical failure (from the chain rub mostly). I was thinking about glueing the cover to the rim but I haven’t come across a recipe for doing this, but your mentioning electrical tape gives me some ideas. I’d like to see how it’s done by others more experienced with this.
So do I, but I’m not sure what you mean by chain rub. Not a problem for me. I’m using a Mavic GL330 tubular rim with dura-ace hubs.
That’s basically the same as me, I have a DA hub & Mavic MA40 clincher rim. The chain rubs when I’m in my big sprocket. It leaves a light circular mark on the cover but so far has not caused any real problems other than unnerving me a bit when I’m already wrought with race tension.
I don’t spend much time in the low gears for races around here, but I will probably develop male pattern baldness fretting up Richter pass this summer. I could do without that.
Ride your Mavics front and rear and put your $400 towards coaching…
As for the cover, I don’t mean any personal offense, but the argument is always “just as good as a disc”. But, it’s never proven better…not to mention the potential issues with install & use.
I understand people are on a budget and may be appropriate.
I’m not surprised a lot of people chimed in recommending the CH aero cover, but I wonder how many of them actually have any experience with the product and are just repeating the party line they have read here. I’d take YabYum’s advice and not try to make the CH cover work with your Ks. The covers make more sense if you have an extra box rim training wheel around, or have a powertap.
If you are committed to the sport, I’d look to the long term. This year, buy the Renn disk. Then you’ll have a rear wheel that is petty much as good as anyone really needs. Then next year I’d save up your money and watch for a fall or winter coupon sale and buy a good front wheel new when you don’t need it. The prices on ebay aren’t usually spectacular enough to justify the risk of getting second hand wheels. In the end you’ll have great equipment that you won’t regret.
You certainly can use the K front with a disk rear, nothing wrong with that. While Ks certainly give up significant performance to a true aero wheel, the difference is not going to be as large as some make it out to be. (Check the tech section of Zipp’s site for some aero test of the Ks. This year, you can comfort yourself with how much better your Ks are than a 32 spoke wheel. Next year, you can comfort yourself with how much better your new front wheel will be than the K.)
Also look to the long term and decide if you want your race wheels to be sew up or clincher. Clinchers really are fine performance-wise, but if you’re a weight weenie you’ll probably never be happy unless you go for the sew-ups. If you decide sew up, then get the sew up disk. You’ll have to carry a spare tube and tire irons as well as a spare tubie, but this extra ¼ pound is no more than the extra weight penalty you would have had with the CH aero cover instead of the disk. And you can use one of the tire irons to help peel the tubie off the rim if you have a flat on the rear.
