It seems a number of very good UK Testers are switching to Xentis wheels with some now preffering them to a disk on the rear.
Ben Instone rode some to silver in the National 50 1:42:42.
The riders I have talked to seem to think they go quicker with them at a given power than there other aero wheels. I understand the lastest tunnel test show the new ones are up there close to Zipps 808’s but I would still have though that a disk would generally be quicker. Is there anything a wind tunnel doesn’t pick up on a wheel that can effect performance?
weight?
“Road feel.” Lots of time, what “feels” fast is due to rim stiffness, weight, etc. So they may “feel” faster than a disc, but that doesn’t mean they are. However, it is possible that riders feel they corner better than a disc.
disc are faster then 3 or 4 /5 spoke wheels
even the worse disc that i have tested where faster the any of them
the problem also is that all disc are tested with out load
since lot of disc as wheel 3 /4 /5 spoke wheel flex this is a important thing
take a popular disc under racing load they flex more then 2 mm
those disc are not stiff about 50 N/mm
this means lot of aero loss in the wheel ,
i have tested this can go up to 10 watt loss up to 50 km/h
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do you mean the disk flexed 2+mm while riding on level, straight roads or while cornering?
Where does the 10W increase in the power to overcome aero drag come from?
straight roads (±1.mm ) means 2 mm watts extra drag by flex ( measured in wind tunnel ) due to 2 mm flex all at 50 km/h
Ben Instone obviously feels that the Xentis was his quickest rear wheel but in the end he missed out on 1st by only around 20seconds I wonder if he had used a disk if he might have won over 50miles?
So, even with the flex under load, is a disc still faster than a 3/4/5 spoked wheel? How do the 3/4/5 spoked wheels flex at those speeds?
Watch out at IM Canada - Gordos going to be testing a set of Xentis Mark 1 TTs next week with some lovely dugast tubs .
You might see him use them at IM Canada .
As for Ben - hes done a lot of testing with his disc vs the xentis vs all his other wheels (a lot!) , hes no mug , and hes pretty convinced the xentis have the edge .
If theres interest I could ask him to post his test results , and methodology , he might be willing post it .
Yes please!.
ah, another forum for me to waste my time on (-:
the xentis are quick, ive used loads of wheels in the past but for the last couple ive always used my comete disc and 808 for important events as they have been the quickest (even on hilly courses). Now ive sold the 808 and only use the comete for club events and days where i just fancy a change. If im after a quick time its the xentis.
The problem with tunnel test is that they are to controlled, wind never just comes at you from one angle at a constant speed, the wheel is never perfectly upright and not swaying around like it is on the bike, they dont take road surface/vibrations into account or hillsand more important they dont tell you how they feel. You can make the fastest wheel aerodynamically but if it impossible to control then its usless.
ive done a load of test over a 2 mile stretch of road with different wheels and the best ones ive found (comete, xentis TT, xentis mark1 HM) i then used over a ten mile TT, i rode the course at the same power with the HM’s, comete rear and TT front and with a pair of TT’s. I did this within and hour with just enough time to swap wheels between runs so changes in weather were kept to a minimun and the result, The comete felt the quickest but the TT’s were the quickest and the HM where very close behind.
Another interesting thing was that i was alot smoother using the TT’s, i would of thought the extra weight/momentum of the disc would keep things smooth and thats how it felt but the power spread was much wider with the comete
Firstly, welcome to ST.
What kind of weather do you do most of your ‘base tests’ in? I’m assuming it’s not windy as it would be difficult to keep the power constant. How do they handle/perform in side winds? just wondering as the Xentis Mark 1’s did not perform very well in the tunnel when the yaw angle was increased.
done in both still and very windy conditions. Mark1’s are fine in cross winds, no handling problems, TT’s are scary in strong cross winds when going slow but get better the faster your go and still out perform the comete. Interestingly the TT on the front is easier to handle with a disc on the back in strong cross winds.
As for speed, still days with no wind or dead head tail TT’s win everytime, cross winds kinda to close to call on smooth flat roads, but on rough or hilly roads TT’s win again. I am talking a handfull of seconds here not minutes
when i rode the 10mile TT with the wheels i aimed to average about 430watts as i can do repeated runs at that without fatigue kicking in, every run the ave power was within 5watts of that wind or no wind.
i should say i love the comete, its a great wheel and i never thought id race on anything else and i had to do alot of test before i was brave enough to race on the xentis. Oh i also think the comete is the fastest disc ive used, and ive used most