Brompton really doesn't like anything other than smooth surfaces

[bence8810]

I have the Brompton standard kevlar tires (I think - whatever comes stock on a 2016 year-end bike) and it is inflated to 100PSI.
It shakes the living daylight out of me, I just got the bike a week ago and hope to get used to it but it just feels wrong. Can't be good for the bike either, all the shaking...

I have the firm suspension. Just got a track pump, it was delivered today and will try to go down to 80 and see. The tire is clearly marked as "inflate to 100PSI"....

Ben

 

[jay clock]

If you have a front bag with stuff in I find the handling improves

 

[Kell]

Mine definitely rolls a little easier with less air in the tyres.

And there's evidence to support that a wider tyre (and rim) at a lower PSI is faster than a thinner tyre with higher PSI.

View: https://www.youtube.com/watch?v=yrHxQg1OW0A

 

[12boy]

The above are all correct...unfortunately with the exception of Greenspeed scorchers there isn't anything wider than 1 3/8 available nor will it fit. Ergon grips are nice and I've wrapped my old cork ones which were falling apart with some cork tape which also helps. Having bar ends is good also as your hand position changes. Weight in the front basket really changes things for the better and you can experiment with the height, angle and fore and aft saddle position to move pressure from hands to butt. I like around 70 psi , too, and if there is more rolling resistance it seems negated by the softer tire not bouncing around so much. To some extent you can unweight yourself from bars and saddle when riding over gnarly sections and let your legs soak up the bumpiness.

 

[SkipdiverJohn]

Tyre pressures should be set according to the amount of weight being taken by each wheel, not some arbitrary figure front and rear. I don't like the way Bromptons and other small wheel bikes ride, so I don't own one, but the tyre pressure issue is the same for all bikes. The front tyre should always be run at a lower pressure than the rear, as it carries less load and therefore doesn't need to be so hard. There are sources of information on the 'net that have useful tyre pressure charts for different loads and tyre widths. The starting point for any pressure experimentation is rider weight, bike weight, any extra load carried, and handlebar configuration. That gives an approximate front/rear weight distribution, generally about 40%/60% with an upright riding position. Then you look at the tyre width, and select a suitable pressure for that size tyre with whatever load it carries. I run all my bikes with the front tyre pressure approx. 75% of the rear tyre. If you run overly hard front tyres you get a hell of a lot more vibration transmitted to the hands and arms through the bars and on bad surfaces this can be very unpleasant on anything but very short rides.

 

[rogerzilla]

Bromptons have only about 1/4 of the weight on the front wheel (depending on saddle position) and can give you a nasty surprise if you go to hop up a kerb and the bike does a full wheelie.

Tyre suppleness is very important and something with thick sidewalls and an inflexible tread will be punishing. The Brompton tyres aren't bad.

The titanium fork makes things a bit plusher but you probably didn't want to hear that.

 

[Tenkaykev]

Interesting thread. I've just started riding a Brompton, my only recent cycling experience being about half a dozen short trips over as many years on a hybrid bike I inherited from my wife. The Brompton is a 2nd hand 2015 M6L, I recently took it in to the local dealer to have the bottom bracket changed as it was in the recall. While there I had the tyres changed to Marathon Plus.

I went a bit off course on my way back from the LBS and ended up riding along gravel / gritty trails through the local country park. The ride was " interesting " in that it felt a bit skittish. I found the need to be careful on cycleways where the tarmac has started to rise due to tree roots. I also noticed that the seat post was very gradually creeping lower. I reset it to the correct height and made sure the clamp was tight. A little while later it started to creep down again. I suspect this might be my own fault as after I had cleaned it I decided to use furniture polish all over to make it nice and shiny

With the Marathon Plus I can see that the tyre is being compressed slightly by the frame when closed, is this something to be concerned about. I have about 90psi in the front and 100 in the rear tyre, perhaps less air might help?

EDIT: My mention of the tyre pressure has got me thinking about the accuracy of the pressure gauges on track pumps? I use my wife's pump labelled " Bike Hut " and have assumed the gauge to be accurate.

 

[12boy]

In my understanding the tire pressure indicated on a tire is the upper limit, not what you must have. Some tires have a range, e.g. 55-75 psi. Go too low and the tire can squirm on the rims and/or cause snakebite punctures. Go to the limit listed and your hands can suffer and you can lose traction on slick surfaces. You can always change your pressure to accomodate the ride you are expecting.

 

[Pale Rider]

Interesting thread. I've just started riding a Brompton, my only recent cycling experience being about half a dozen short trips over as many years on a hybrid bike I inherited from my wife. The Brompton is a 2nd hand 2015 M6L, I recently took it in to the local dealer to have the bottom bracket changed as it was in the recall. While there I had the tyres changed to Marathon Plus.

I went a bit off course on my way back from the LBS and ended up riding along gravel / gritty trails through the local country park. The ride was " interesting " in that it felt a bit skittish. I found the need to be careful on cycleways where the tarmac has started to rise due to tree roots. I also noticed that the seat post was very gradually creeping lower. I reset it to the correct height and made sure the clamp was tight. A little while later it started to creep down again. I suspect this might be my own fault as after I had cleaned it I decided to use furniture polish all over to make it nice and shiny

With the Marathon Plus I can see that the tyre is being compressed slightly by the frame when closed, is this something to be concerned about. I have about 90psi in the front and 100 in the rear tyre, perhaps less air might help?

EDIT: My mention of the tyre pressure has got me thinking about the accuracy of the pressure gauges on track pumps? I use my wife's pump labelled " Bike Hut " and have assumed the gauge to be accurate.


View attachment 436776

A dealer told me he had a Brompton which would not fully fold unless the tyres were deflated.

He couldn't find anything else wrong with it, so concluded the geometry/clearance for tyres when folded varies on some bikes.

Or some tyres are taller than others.

 

[Kell]

In my understanding the tire pressure indicated on a tire is the upper limit, not what you must have. Some tires have a range, e.g. 55-75 psi. Go too low and the tire can squirm on the rims and/or cause snakebite punctures. Go to the limit listed and your hands can suffer and you can lose traction on slick surfaces. You can always change your pressure to accomodate the ride you are expecting.

The tyres on my road bike have a range (which is ridiculously high 115-175 IIRC).

But the Marathon pluses state 90. Mine feel more comfortable around 75-80.

 

[Banjo]

Got 70psi front and back on mine.(Marathon Racers on my brommie are marked :inflate 65 to 110 psi).
I Dont go off road but some roads I use are pretty rough.Willing to sacrifice a tiny bit of speed for extra comfort.
At 110psi I think my fillings would fall out.

 

[Banjo]

[QUOTE="

I went a bit off course on my way back from the LBS and ended up riding along gravel / gritty trails through the local country park. The ride was " interesting " in that it felt a bit skittish. I found the need to be careful on cycleways where the tarmac has started to rise due to tree roots. I also noticed that the seat post was very gradually creeping lower. I reset it to the correct height and made sure the clamp was tight. A little while later it started to creep down again. I suspect this might be my own fault as after I had cleaned it I decided to use furniture polish all over to make it nice and shiny
[/QUOTE]
No matter how tight I had the QR clamp the seatpost on mine used to slip down a bit when the bike was new but doesn't do it now. Possibly the makers wiped a bit of oil on it .

 

[bence8810]

With the Marathon Plus I can see that the tyre is being compressed slightly by the frame when closed, is this something to be concerned about. I have about 90psi in the front and 100 in the rear tyre, perhaps less air might help?

Just checked mine, the tyre is indeed touching the frame when folded and is being compressed. Maybe all bikes are like that! I have the Brompton factory tyre (Kevlar?) at 100PSI.

I don't keep mine folded much, only when in transit which happens a few times a month, at home I am in the "parked" position. I saw the tyre is touching even when parked but just barely, once can still move the wheel.

I am going to put some helicopter / clear tape on my frame where the tyre / cables touch to keep the paint, I found this tip yesterday while reading.

Cheers,
Ben