Numpty IM Bike Thread - Page 577 - Triathlon

fat buddha

20/04/2012 at 17:02

stiffness is no big deal - if they're built well, they're stiff at any depth

fwiw - I run 60 front, 90 rear and did IMWales on them (and a few other IM). the only thing you need to be wary of with deep rims is wind - and at IMW last year it was vicious wind so handling at times became an issue. the roads at IMW often have high hedges which shelter you but then you'll get a gust coming through a gate opening which would send you across the road - that caused a few people to crash.

being a large munter, I can keep the back end down better in wind than the skinny whippets so it wasn't as big a deal for me.

but in hindsight - did I gain anything from them at IM over that lumpy course? probably not and standard rims would have been more stable on the day and I don't think I'd have lost any time with them.

deep rims are great when the course and conditions are right but they ain't always necessary.

IronCat5 in the Hat pirate

pirate

20/04/2012 at 17:55

I'm also looking at the PX 50 & 60mm wheels. 60mm are like hen's teeth.

How do these disc-covers fare? Is it a good spend for £80, or am I likely to end up blown in to a field. I'm guessing Marshman could be a lot windier than Outlaw.

SwimsLikeAWalrus

21/04/2012 at 09:50

I find the 50s a handful in the wind. I also prefer my road bike's rim for lunatic descendng too!

I'm just a scaredy cat!

popsider

21/04/2012 at 10:29

You'll be fine with disc covers Cat - it's the front that affects handling - if it's OK to use a 50mm in the front you'd be OK with a disc in the rear.

My deep sections aren't super deep - think they are about 45mm - but not had a problem with them in even quite windy weather - for a triathlon I reckon all carbon for the weight and then maybe 50-60mm front should be OK on 90% of days if you are reasonably confident on a bike - maybe stay 40-50mm if you are nervous or getting blown about.

If you have the money some of the modern rim shapes (Zipp,Hed for two) are meant to be far more stable in cross winds and provide more aero benefit when the wind is from an angle.

I'm looking at getting some new deep sections but more for road races so looking at something with an alloy brake track as I don't like the grabby braking you get on some (like my current ones) call carbons - doesn't seem to bother some people mind you.

slowerthanilook

23/04/2012 at 11:54

Thanks folks. I've treated myself to a cheap pair of clincher 60's. Will stick a 12:27 cassette on the back and try that out as race set-up. See if I can stay out of the ditches on them!

IronCat5 in the Hat pirate

pirate

23/04/2012 at 17:44

Which ones did you get Slower? The PX handbuilts?

Golden Boots pirate

pirate

23/04/2012 at 19:08

Hmmm... an aero jacket for the PX60mms are tempting. Does anybody know how easy are they to get off and on? Is it a couple of minutes job or does it take a couple of hours or so?

slowerthanilook

24/04/2012 at 10:09

I went even further down the cheapskate league than that, Cat. Direct from carbonzone in China via ebay. The shame of it

. Could have gone cheaper still, but the overwhelming majority of blog and forum feedback on carbonzone seems positive, so I live in hope. I'll let you know how they work out.

IronCat5 in the Hat pirate

pirate

24/04/2012 at 11:24

That was my orignal choice. Was looking at the full carbon 50 and 80.

Are yours full carbon or carbon faired?

slowerthanilook

24/04/2012 at 11:37

It says "full carbon" on the receipt. Wondered about getting different sizes for F and B but just went with what looked easy tbh. Asked them to do the nice red hubs and spoke nipples because I'm vain and shallow. Bought separately some Conti Light tubes with the 80mm valve so that I don't have to muck about with extenders. Everything I've read here suggests they're a pain you can do without. Last question I'm toying with is whether to get some custom decals made for them

Pebble 2

24/04/2012 at 16:41

Regarding the wheelcovers, taking them off and putting them on requires you to remove the cassette. So you need tools for that as well as a screwdriver for the jackets screws. It takes me about 5 mins to do the job with the correct tools.

Regarding the Chinese wheels, I've ordered a set direct from the factory, awaiting delivery will let you know when they arrive what they are like quality wise in comparison to my others.

Golden Boots pirate

pirate

24/04/2012 at 17:43

Thanks Pebble, may look to purchase in the forthcoming weeks then

Iron Muffin pirate

pirate

30/04/2012 at 10:33

Morning bike brains.

Please can someone help with my numpty question of the day.

Do inner tubes have a max pressure and if so how do I check?

I inflated my new tyres to 120 (it said upto 140 was okay) and then a tube blew up. It may have been 'pinched' as I had just changed the tube and was wondering if it would have been the extra pressure or my tube chagning numptiness.

fat buddha

30/04/2012 at 10:59

sounds like tube changing numptiness

it's almost impossible to overinflate a tube as it's contained in the tyre - it's the tyre that dictates the max pressure. unless of course there was a fault in the tube, which is not unheard off - I've had a few new tubes refuse to inflate and the problem's usually around the valve, often with a split.

pinch punctures will go at higher pressures so always be careful when putting them in as it's easy to trap the tube between the rim and tyre

one other question - why 120psi?? I'm pretty heavy and rarely go beyond 110psi on my racing wheels - for my training tyres I stick at around 100psi

Iron Muffin pirate

pirate

30/04/2012 at 11:14

Thanks FB.

Why 120 psi? The misguided belief that I may go fatser and get less punctures.

How do I work out the best psi?

popsider

30/04/2012 at 11:56

I stick 115 in the dry - a bit less in the wet - although the Vittorias on my race wheels actually say minimum 120psi !

I wouldn't worry too much - look at the side walls of the tyres and keep them within that range. Heavier riders generally stick more towards the top end of the range in, wet weather or rough roads stick a bit less in.

FB is certainly right that you don't need high pressure - the science suggests closer to 100 you get lower rolling resistance I just prefer the feel of a having them a bit harder(!)

fat buddha

30/04/2012 at 12:02

"How do I work out the best psi?"

based on what others do....

it's somewhat a case of trial and error and experience and you can work within quite a large range but not see that much difference

it's marginal how much quicker you'll go at higher pressures - certainly when you get past 100psi or so. high pressures should mean less tyre contact with the road so more speed, but as pops says, the science here is a bit sketchy. you're also at a greater risk of a pinch puncture should you hit a pothole with high psi (assuming you're not on tubs)).

the other issue with puncture frequency is type of tyre (kevlar reinforced ones tend to be more puncture proof), age of tyre (old ones become thinner so more prone to punctures), tube quality, and of course road surface/debris etc.

Edited: 30/04/2012 at 12:06

Iron Muffin pirate

pirate

30/04/2012 at 13:17

The tyres in question are clinchers, Schwlebe Ultras (?!?) apologies bike aficionados.

Girlie purchase I am afraid.... the matching colour strip did it.

My first pucnture was bizarre and has marked the tyre. No raod debris, nothing in tyre, nothing to explain it. The good thing was how easy the tyre was to change after my last ones that were full of metal strips.

I didnt even cry, swear or take 3 digits worth of minutes.

fat buddha

30/04/2012 at 14:50

probably Schwalbe Ultremo ZX as they come in different colours - some people have complained about them having soft sidewalls and puncturing easily - see here - maybe what you've seen MT??

my everyday training wheels are shod with Continental Gatorskins which are pretty bullet proof until they get well worn.

Iron Muffin pirate

pirate

30/04/2012 at 20:55

That will learn me..........pick tyres with colour stripes to match and run the risk of more punctures.

Will probably take your advice on replacements in a few weeks.