Tyre Pressure

Fatbiker

Hi

I recently bought a new Trek 7.2 fx hybrid for general road cycling, for improving my fitness etc. As my username suggests, I am a large guy, about 21st and 6'2". I find it difficult to get enough tyre pressure into the (back) wheel. I bought an electric pump from Lidl and can get the tyre quite hard but still seems to flatten out a fair bit when I am cycling. Do I need bigger tyres[it's a 26" wheel with Bontrager tyres]? How hard should I pump up the tyre? Am I too fat for this bike?

Thanks,

Fatbiker

Khannie

What pressure do you get it to?

Fatbiker

Khannie wrote: »

What pressure do you get it to?

I have no idea...the Lidl pump doesn't seem to register the pressure on the bike. Then again, I did not read the instructions. FB

serendip

I believe they are probably 700x35c wheels. You don't need bigger wheels. You do really need to know that the pressure is right, though. The max/min pressure should be written on the sidewall of the tire. If you've any cash left, you might want to invest in a track pump.

07Lapierre

You need one of these

I doubt an electric pump would inflate a bicycle tyre to 100psi.

(If im wrong someone will correct me! )

Fatbiker

07Lapierre wrote: »

You need one of these

I doubt an electric pump would inflate a bicycle tyre to 120psi.

(If im wrong someone will correct me! )

Really? 'Cos the bike bounces like sh*t when it's inflated with the electric pump. I can't imagine making it any harder.

Thanks everyone.

kincsem

FB
You need to believe what the posters are telling you about tyre pressure. You don't know what pressure you have in them so you are guessing.

With a hand pump I thought my tyres were pumped hard. Then I got a track pump. The "hard" tyres registered about 35 psi on the track pump gauge. I pumped them up to 120 psi. The bike went quicker. When I ran over a pebble it shot away like a bullet. €30 on a track pump is the best spend.

MagicMarker

Hey OP, those tyres are probably rated for 85 psi. I have the same tyres on my Trek 1.3.

I just got myself one of these, in fact it only arrived today! Pumped up the tyres for the first time to 100psi and they were rock solid, could not even make a dent in them with my thumbs, felt like I went too high tbh.

blorg

120 PSI is a road bike pressure, for narrow tyres. Even then it is on the high side, 100-110 is more optimal for most while lightweights can go lower.

Do NOT put your hybrid tyres up to 120. As you are heavy, you probably want them at the max written on the sidewall, whatever that is. My 700x35s are 50-85. But look for your specific tyre (you say it is a 26.) Lower pressures in wider tyres.

newballsplease

Is it common for a Presta Valve to break off in a pump? I didnt think there was any particular way of putting a pump into a valve? i thought just shove it on and pump away? should it be sorta screwed in?
im serious here... but(try reading that without it sounding dirty!)

Fatbiker

Guys, it is clear I will have to get a track pump! Is there no end to the amount of cra*p I will keep buying for the biking? .. I am ordering something every few days off eBay or Wiggle or whatever...or picking things up in Lidl.

Thanks for all the good advice.

Seem to have a slow puncture in back wheel. Cannot detect it with basin of water. Very awkward to work on back tyre due to gears, hub etc. Of course I should have taken the tube out on the off side so as not to have the chains interfering but you lives and learns.

Any tips for detecting the slow puuncture?

Ta, FB:D

seamus

Fatbiker wrote: »

Any tips for detecting the slow puuncture?

First off, flip the bike over (put down two mats to rest the handlebars and saddle on) and remove the back wheel. Fixing punctures with the wheel still on the bike is for the olden days before quick release. It'll be way quicker and cleaner off the bike. http://www.jimlangley.net/wrench/removerearwheel.html

Shouldn't really need a basin of water for a slow puncture unless it's really slow (like over a couple of days).

Remove the tube completely and inflate it. Not too much, but the whole tube will swell. This will cause any hole to stretch out a little bigger and make it easier to detect. My method for finding them is to find a quiet place and then hold the tube right up to my ear, listening along the whole length for a hissing sound. Your ear is also quite touch-sensitive, so you will likely feel the air blowing on it too.

manwithaplan

blorg is right about the hybrid tyres. They are usually 700x35. The ones that came with my bike had a recommended pressure of 60-80 psi. Look at yours and pump them to the upper end of the recommended range as you are a big guy.

Also you're better off taking the wheel off when fixing a puncture, even if you are only going to patch it rather than replace the tube.

Donie75

Fatbiker,
I have a Trek 7.2fx as well as a road bike. The wheels are quick release so pop the back wheel off and follow this article for instructions. http://www.bikeradar.com/gear/article/workshop-how-to-repair-a-puncture-30614
From what you're saying it sounds like you're trying to find the hole in the tube with the back wheel still attached.

Fatbiker

seamus wrote: »

First off, flip the bike over (put down two mats to rest the handlebars and saddle on) and remove the back wheel. Fixing punctures with the wheel still on the bike is for the olden days before quick release. It'll be way quicker and cleaner off the bike. http://www.jimlangley.net/wrench/removerearwheel.html

Shouldn't really need a basin of water for a slow puncture unless it's really slow (like over a couple of days).

Remove the tube completely and inflate it. Not too much, but the whole tube will swell. This will cause any hole to stretch out a little bigger and make it easier to detect. My method for finding them is to find a quiet place and then hold the tube right up to my ear, listening along the whole length for a hissing sound. Your ear is also quite touch-sensitive, so you will likely feel the air blowing on it too.

I was afraid to take off the wheel as I don't know how to set the gear chain to the right tension.or do I have to? Really, I clearly know **** about this game, it's been 35 years and bikes were simpler then, I think! Thanks Seamus, I will try it. FB

PS: Fantastic link Seamus! Printing that and bookmarking the site....

Fatbiker

Donie75 wrote: »

Fatbiker,
I have a Trek 7.2fx as well as a road bike. The wheels are quick release so pop the back wheel off and follow this article for instructions. http://www.bikeradar.com/gear/article/workshop-how-to-repair-a-puncture-30614
From what you're saying it sounds like you're trying to find the hole in the tube with the back wheel still attached.

Yes, I am/was. Thanks for the link. I actually removed one brake block in order to get the tube freed up! Oh God! What a Muppet!:o

manwithaplan

Don't worry about taking off the back wheel. You won't have to do any adjustment on the chain or derailleur. Shift into the biggest front chainring and the smallest rear sprocket (both of these are the ones furthest from the frame). You may have a quick release lever on the wheel or you might have an allen key bolt. Whichever it is, loosen it and then hold the plastic nut on the other side while you undo it a bit more - if it's a quick release level, open it before you rotate it. Unhook your rear brake and push the wheel down out of the dropouts - the little metal recesses on the frame that the wheel sits into (or pull the wheel up if you have the bike upside down!). It should just come right out but you can use your hand to move back the derailleur cage (the two little wheels) if it seems to be in the way. You could also loosen the nut or quick release a bit more if it seems stuck.

When you have fixed the puncture, put the wheel back on, lining up the smallest sprocket with the chain. You then should be able to just push it into the dropouts again. Tighten up the quick release lever or bolt. If it's an allen key bolt just screw it in tight but if it's a quick release, rotate it to the point where there's enough resistance to leave an imprimt in your palm when you close it. Don't overtighten it - you shouldn't have to exert any real force to close it. Hook your brake on again, spin your pedals just in case the chain is on the wrong sprocket and you're good to go.

seamus

manwithaplan wrote: »

Tighten up the quick release lever or bolt. If it's an allen key bolt just screw it in tight but if it's a quick release, rotate it to the point where there's enough resistance to leave an imprimt in your palm when you close it. Don't overtighten it - you shouldn't have to exert any real force to close it.

Quick tip for doing up quick release bolts;

Put the lever into the closed position from the start and then screw in the opposite side so that it's fully hand-tightened. Then open the lever fully and turn the opposite side again, between one-quarter and one-half turn, before closing the lever again.

seven stars

blorg wrote: »

120 PSI is a road bike pressure, for narrow tyres. Even then it is on the high side, 100-110 is more optimal for most while lightweights can go lower.

Do NOT put your hybrid tyres up to 120. As you are heavy, you probably want them at the max written on the sidewall, whatever that is. My 700x35s are 50-85. But look for your specific tyre (you say it is a 26.) Lower pressures in wider tyres.

Does that apply to any hybrid? I have a Specialized Sirrus Sport with 700x28s, and I've got them rock hard at around 115 (pretty sure I saw that written on the side of the tyres). I'm roughly 12.5-13 stone.

seamus

You can pretty much ago as high as the maximum rated pressure on the sidewall. 115 sounds a bit high for 28s. I run my 23's at 110PSI and I'm heavier than you.

blorg

You can go as high as is rated but 115 is pointless for 28s. I ran mine around 80/90 IIRC. You need more in the back. Higher pressure beyond a certain point is actually slower as well as less comfortable.

07Lapierre

seamus wrote: »

Quick tip for doing up quick release bolts;

Put the lever into the closed position from the start and then screw in the opposite side so that it's fully hand-tightened. Then open the lever fully and turn the opposite side again, between one-quarter and one-half turn, before closing the lever again.

Good tip, and just to add to it, just before you close the lever, apply the brake, then close the lever. this will "center" the wheel at the same time as tightening it.

Paul Kiernan

Based on this chart the OP would need about 80psi rear, 75 psi front on his 35c's and seven stars about 90psi, 75psi on his 28c's.

seven stars

Fair do's, cheers for the help.

Fatbiker

Paul Kiernan wrote: »

Based on this chart the OP would need about 80psi rear, 75 psi front on his 35c's and seven stars about 90psi, 75psi on his 28c's.

Thanks although I don't understand this chart stuff.FB

\gonna borrow a track pump tomorrow. FB

Fatbiker

Update: Thanks to the fantastic help on here, I took off back wheel, found a track pump in bought in Aldi a couple of years ago and fixed the puncture (twice! - think I patched the wrong side of the tube first time or there were two punctures at same site). Pumped up both tyres to 80psi, which the max on tyrewalls, they are 700x35s btw. I could not believe how hard they became - no way I could have done that with a typical bike pump. Got wheel back on no problem. However, as I had removed a brake block:mad: to free up the tube when I was trying to fix it while still on wheel, I then tried to close the brakes by slipping the noodle back into the holder but I could not so I loosened the cable end and eased the tension, got the noodle back in but find it hard now to tighten up the cable again. As a result the brakes are locked on!

Can anyone tell me a handy way to ease the brakes tension and fee up the wheel? Sorry to be such a numpty but I am learning fast.

FB:o

blorg

There should be a barrel adjuster on the shifters that allows you to change the cable tension. If that isn't enough you can loosen the Allen bolt holding the cable to the brake, give it just a tiny bit more cable, and retighten. But that should not b necessary presuming they worked before. To be honest I think it is more likely you didn't reseat the noodle correctly or something; they should go back on exactly as they were before, not grabbing the wheel. If the noodle wasn't quite seated in the socket they would grab the wheel though.

Fatbiker

blorg wrote: »

....To be honest I think it is more likely you didn't reseat the noodle correctly or something; they should go back on exactly as they were before, not grabbing the wheel. If the noodle wasn't quite seated in the socket they would grab the wheel though.

Spot on Blorg.In re-attaching the brake block I had piled on too many washers/spacers on the rim side so it was too tight to the rim. When I studied the other side and the front wheels I realised what I had done so I re-did the block again and hey presto, I was able to re-adjust the tension in the cable and noodle thing no problem. Then the front wheel was rubbing but that was quickly narrowed down to the mudguard being too close now that the wheel is up at 80psi - I still can't believe it, I can't wait to get out on the bike to see what difference it makes. Just took mudguard off and will bring it into shop when getting bike serviced soon.

Many thanks for all the help especially from those so far away. I will be back....Fatbiker;)

serendip

Fatbiker wrote: »

(twice! - think I patched the wrong side of the tube first time or there were two punctures at same site).

Sounds like a pinch flat: http://www.sheldonbrown.com/gloss_p.html#pinchflat

Pinch flats are usually caused by under-inflated tyres.

Fatbiker

serendip wrote: »

Sounds like a pinch flat: http://www.sheldonbrown.com/gloss_p.html#pinchflat

Pinch flats are usually caused by under-inflated tyres.

Yes, that makes sense.

On a broader note - WOW! Shaved 5 minutes off my usual turn point, from 29 to 24 mins, proceeded on then to my personal Col de TOURMALET, a village up a long slope. Made it in 38 mins, first time to reach the village! Really chuffed. Tyre pressure made all the difference. Going out again this afternoon. Thanks again guys, you have opened my eyes and made the cycling a lot more enjoyable. Cheers!:D:D:D

Fatbiker