Bike Skittish on GP4000s - what did I get wrong?

cattytown

Having heard much good stuff about the 4000s I decided to give them a try on my Defy 2.

I found the bike very skittish on them, and felt like I really had to keep on top of it. Putting the standard tyres back calmed the bike back down.

So I see one of two things - either I got something wrong like the 4000s like different pressures - they looked centred OK, or that's how a bike is supposed to handle and the standard tyres slow things down.

Any thoughts?
Thanks.
Paul.

sungod

there can be big differences in feel between tyres

gp4000s tyres are pretty grippy, maybe you had the pressure too high, or perhaps the old tyres were simply fatter/squishier

what size gp4000s? what pressure front/back? how heavy are you?

what type/size/pressure were the old tyres?

turnerjohn

if you werent down in size or changes to pressures could make a difference....otherwise GP4000s about as grippy as you can get !

desweller

How far did you go on them?

New tyres often have some of the mould release agent on the surface; you need to clean it off before use or the tyre will be a bit slippy.

cattytown

Thanks for the comments, I'll ry to answer as well as I can!

same size as previous tyres (700*23) previous tyres being the stock Giant tyres (S-R4?). Both brands inflated to around 110 psi (not done anything scientific about trying to work out optimum) and I am a larger rider 16st4, 226lb, 103kilos.

I didn't feel a problem with grip - if anything the feeling meant grip would be less of an issue as I would hold back even more! The much vaunted grip was one of the esos for trying them, and as I say I feel I got something wrong :-(

I had them on a couple of hundred miles, so gave them a moderate chance.

dee4life2005

GP4000s are directional ... did you put them on the wrong way ? Don't think it would make much difference though.

cattytown

I looked but didn't see a directional marking - where is it and what form does the making take?

cattytown

A google search finds http://foter.com/f/photo/5265639052/18c1517405/

wishitwasallflat

Give them a good scrub with warm soapy water - then a rub over with sandpaper and then rinse them off and try them again.

cattytown

I'll give them another try, but I have a couple of big for me rides coming up, so no unforced changes now - gash a tyre and maybe I'll try them, but not until.

I was just king of hoping I'd get a response like "jeez what a newb - *everyone* knows you run GP4000S at 15 below a normal tyre" or something similar.

Paul.

sungod

110psi front is going to feel harsh unless the road is smooooth, try 95, look to see if the tyre is deforming visibly, if it is go to 100

but tbh at > 100kg for you+bike i'd run wider tyres, at least 25mm, maybe 28mm at the rear if there's clearance

if you ran 25/28mm front/rear you could use 95psi/110psi, drop it 5psi for wet days or if it still seems a bit harsh

you could keep 23mm on the front to get your money's worth out of the 23s

cattytown

I'm hoping to sort the loading the other way - reducing the load :-)

I might try the lower pressures, but the higher pressures seem OK with the std tyres...

cycleclinic

The heavier the rider the higher the pressure that is needed. 110 psi should be fine. I ride with that pressure and I am alot lighter. I cannot say I feel the ride too harsh and the grip is as much as I need.

Wider tyres never hurt though. 25mm on the rear is a good call.

Bordersroadie

25c GP4000s are a a magic carpet ride, faster and lower resistance on bumpy roads than 23c. They weigh virtually the same as the 23c. I wouldn't even consider 23c at my 74kg never mind 100+.

apreading

Even though both tyres have the same size written on them, they may be quite different in reality...

My GP4seasons 28mm rear tyre is more like a 26 - looks about 1mm wider than my 25mm GP4000S on the front, if that.

At your weight, I wouldnt even consider 23mm tyres - not on our roads... Useful article here: http://www.roadiemanila.com/2013/03/rev ... s-23c.html

eddiefiola

about the same weight 100kgs and went from Schwalbe Lugano to GP4000s and they felt great, no probs at all, fast and grippy, although ive just realized i have them on the wrong way according to the Rotation markings

apreading

I am going to have to check the direction of mine tonight - not sure if I realised they were directional when I put them on...

thescouselander

I have a Defy 2 and run the same tyres with no problems. As others have said you probably need to look at the tyre pressures.

sungod

cattytown wrote:

I'm hoping to sort the loading the other way - reducing the load :-)

I might try the lower pressures, but the higher pressures seem OK with the std tyres...

with 23mm and >100kg the 'correct' pressure is way higher, but it's not usually practical, at lower pressures with a narrow tyre the risk of pinch flats increases

the advantage of wider tyres is that they can be run at lower pressure for a given load

if you're going to drop weight then you can persevere with the 23mm, but if you do need to replace one i'd still go to 25mm on the rear at least, it'll just be better

btw while there is a direction arrow on gp4000s it makes no real difference which way you mount them, i use them myself, imho it's just marketing tarting up the sidewall

hstiles

The GP4000s do feel softer than cheaper tyres. I'm around 10-12 kg lighter than you but I run mine at 120psi. The directional tread is mainly for rolling resistance and water dispersal. I was probably running mine the wrong way round for ages before spotting my mistake.