custom bike, psi question
#1
the commutor / tourer
Thread Starter
Join Date: Aug 2004
Location: jacksonville fl
Posts: 626
Bikes: trek 6700 turned touring machine, giant TCR2
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 1 Time
in
1 Post
custom bike, psi question
I have a trek 6700 mountain bike frame that I completely rebuilt into a road touring bike. Right now 100% of my ride time is on paved roads. Just getting back into bike shape so I am not touring... No heavy loads other then myself and one trunk bag.
I have 26 x 1.5 road tires on it that can take up to 100PSI. Sun Rhyno Lite 36 hole rims (these things seem to be bullet proof)
I am 6'3" and weigh 250 lbs. Average rides are 40 miles
What PSI would you recomend I keep the tires at with this rig and why?
Thanks,
Mikey
I have 26 x 1.5 road tires on it that can take up to 100PSI. Sun Rhyno Lite 36 hole rims (these things seem to be bullet proof)
I am 6'3" and weigh 250 lbs. Average rides are 40 miles
What PSI would you recomend I keep the tires at with this rig and why?
Thanks,
Mikey
__________________
"Ready to retire, just can't afford it yet!"
"Ready to retire, just can't afford it yet!"
Last edited by mcavana; 01-11-12 at 05:53 PM.
#2
Senior Member
Join Date: Oct 2007
Location: West Yorkshire, United Kingdom
Posts: 5,773
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 453 Post(s)
Liked 104 Times
in
87 Posts
100PSI, if that's what the tire recomends, if it's too hard or soft you will know within a few minutes of riding.
You may want to look at some tires with a larger volume, from what you have said about the ones fitted, they are high pressure road tires, if you got more touring optimalized, say a 26 x 2.0 this may give you a more comfortable ride without loosing any speed, as you can run it at a lower pressure.
Looking at the rim you are using, how does the 1.5 sit on it? as Rhyno Lites are fairly wide rims.
You may want to look at some tires with a larger volume, from what you have said about the ones fitted, they are high pressure road tires, if you got more touring optimalized, say a 26 x 2.0 this may give you a more comfortable ride without loosing any speed, as you can run it at a lower pressure.
Looking at the rim you are using, how does the 1.5 sit on it? as Rhyno Lites are fairly wide rims.
Last edited by jimc101; 01-11-12 at 06:00 PM.
#3
Bianchi Goddess
Join Date: Apr 2009
Location: Shady Pines Retirement Fort Wayne, In
Posts: 29,682
Bikes: Too many to list here check my signature.
Mentioned: 190 Post(s)
Tagged: 2 Thread(s)
Quoted: 2896 Post(s)
Liked 2,785 Times
in
1,441 Posts
^ what he said. whatever the tire recomends on the side.
__________________
“One morning you wake up, the girl is gone, the bikes are gone, all that's left behind is a pair of old tires and a tube of tubular glue, all squeezed out"
Sugar "Kane" Kowalczyk
“One morning you wake up, the girl is gone, the bikes are gone, all that's left behind is a pair of old tires and a tube of tubular glue, all squeezed out"
Sugar "Kane" Kowalczyk
#4
Senior Member
Join Date: Jun 2007
Location: A Coffin Called Earth. or Toronto, ON
Posts: 12,258
Bikes: Bianchi, Miyata, Dahon, Rossin
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Likes: 0
Liked 5 Times
in
5 Posts
15% tire sag rule or max psi on sidewall, whichever comes first.
__________________
Food for thought: if you aren't dead by 2050, you and your entire family will be within a few years from starvation. Now that is a cruel gift to leave for your offspring. ;)
https://sanfrancisco.ibtimes.com/arti...ger-photos.htm
Food for thought: if you aren't dead by 2050, you and your entire family will be within a few years from starvation. Now that is a cruel gift to leave for your offspring. ;)
https://sanfrancisco.ibtimes.com/arti...ger-photos.htm
#5
Senior Member
Join Date: Dec 2010
Location: Above ground, Walnut Creek, Ca
Posts: 6,681
Bikes: 8 ss bikes, 1 5-speed touring bike
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 86 Post(s)
Likes: 0
Liked 4 Times
in
4 Posts
i increase pressure until i can live with the number of pinch flats i'm experiencing. then i adjust to taste for ride comfort. i'm never close to max psi as recommended by the manufacturer.
#6
Lover of Old Chrome Moly
Join Date: May 2011
Location: NW Minnesota
Posts: 2,949
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 143 Post(s)
Likes: 0
Liked 23 Times
in
17 Posts
I appear to be in the minority, but I often run the max recommended pressure, sometimes even a few pounds over. Depends on the bike and the tire. I run higher pressure on pavement than I do offroad or mixed riding.
#7
Senior Member
https://docs.google.com/spreadsheet/...hl=en_US#gid=0 This should give you the 15% drop that is considered proper. This is another source with an explanation. https://www.adventurecycling.org/res...SIRX_Heine.pdf
The sidewall pressure is 1/2 that which will blow the tire off of the rim.
The sidewall pressure is 1/2 that which will blow the tire off of the rim.
#8
Senior Member
Join Date: Feb 2004
Location: St Peters, Missouri
Posts: 30,225
Bikes: Catrike 559 I own some others but they don't get ridden very much.
Mentioned: 16 Post(s)
Tagged: 0 Thread(s)
Quoted: 1572 Post(s)
Liked 642 Times
in
363 Posts
All rims aren't the same. Sheldon Brown (who has repeated that statement on his website) also has a chart listing appropriate rim width vs. tire width combinations. If the "1/2 blow off pressure" staetment were true, there'd have to be a test rim associated with it.
#9
Senior Member
Join Date: Jun 2007
Location: A Coffin Called Earth. or Toronto, ON
Posts: 12,258
Bikes: Bianchi, Miyata, Dahon, Rossin
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Likes: 0
Liked 5 Times
in
5 Posts
narrower rims are more likely to split open with fatter tires inflated to higher pressures.
schwalbe, for instance, recommends that you not inflate really fat tires to the max psi when using narrower rims than recommended for the tire.
conversely, that means wider rims are more likely to withstand such inflation pressures.
schwalbe, for instance, recommends that you not inflate really fat tires to the max psi when using narrower rims than recommended for the tire.
conversely, that means wider rims are more likely to withstand such inflation pressures.
__________________
Food for thought: if you aren't dead by 2050, you and your entire family will be within a few years from starvation. Now that is a cruel gift to leave for your offspring. ;)
https://sanfrancisco.ibtimes.com/arti...ger-photos.htm
Food for thought: if you aren't dead by 2050, you and your entire family will be within a few years from starvation. Now that is a cruel gift to leave for your offspring. ;)
https://sanfrancisco.ibtimes.com/arti...ger-photos.htm
#10
rebmeM roineS
Join Date: Jan 2006
Location: Metro Indy, IN
Posts: 16,215
Bikes: Bacchetta Giro A20, RANS V-Rex, RANS Screamer
Mentioned: 15 Post(s)
Tagged: 0 Thread(s)
Quoted: 653 Post(s)
Liked 345 Times
in
225 Posts
__________________
Bacchetta Giro A20, RANS V-Rex, RANS Screamer
Bacchetta Giro A20, RANS V-Rex, RANS Screamer
#11
the commutor / tourer
Thread Starter
Join Date: Aug 2004
Location: jacksonville fl
Posts: 626
Bikes: trek 6700 turned touring machine, giant TCR2
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 1 Time
in
1 Post
Thanks for all the help guys.
More info:
The tires are "Kenda KWest High Pressure" 26 x 1.5. Max pressure 100psi. Not sure of minimum pressure, I am at work now and forgot to look.
They are only about 2 weeks old. I have been riding them at 100psi. The reason for this thread is I am thinking I should not have the pressure so hi. While the bike is nice and fast, it is a rougher ride... and the other night, while doing a night ride I dumped the bike pretty bad. I was doing a u-turn at about 1 mile per hour at the end of a culdesack and my front tire hit some loose sand on the road. It slipped right out from underneith me. I couldn't get my foot unclipped fast enough and fell right over on my left side.
With the chart provided to get the 15% sag number... what mm would these tires be? LOL, I guess I have been out of the loop for too long... I have never heard of having different tire pressures in the front vs the back... guess it makes sense though. The majority of the weight definately rides on the rear wheel.
I will consider a bigger tire next time for more comfort... but first I got to wear these out!
More info:
The tires are "Kenda KWest High Pressure" 26 x 1.5. Max pressure 100psi. Not sure of minimum pressure, I am at work now and forgot to look.
They are only about 2 weeks old. I have been riding them at 100psi. The reason for this thread is I am thinking I should not have the pressure so hi. While the bike is nice and fast, it is a rougher ride... and the other night, while doing a night ride I dumped the bike pretty bad. I was doing a u-turn at about 1 mile per hour at the end of a culdesack and my front tire hit some loose sand on the road. It slipped right out from underneith me. I couldn't get my foot unclipped fast enough and fell right over on my left side.
With the chart provided to get the 15% sag number... what mm would these tires be? LOL, I guess I have been out of the loop for too long... I have never heard of having different tire pressures in the front vs the back... guess it makes sense though. The majority of the weight definately rides on the rear wheel.
I will consider a bigger tire next time for more comfort... but first I got to wear these out!
__________________
"Ready to retire, just can't afford it yet!"
"Ready to retire, just can't afford it yet!"
#12
rebmeM roineS
Join Date: Jan 2006
Location: Metro Indy, IN
Posts: 16,215
Bikes: Bacchetta Giro A20, RANS V-Rex, RANS Screamer
Mentioned: 15 Post(s)
Tagged: 0 Thread(s)
Quoted: 653 Post(s)
Liked 345 Times
in
225 Posts
1.5" is about 40mm.
I run much lower pressure in the front tire on my long wheelbase recumbent. Front/rear weight distribution is about 30%/70%.
I run much lower pressure in the front tire on my long wheelbase recumbent. Front/rear weight distribution is about 30%/70%.
__________________
Bacchetta Giro A20, RANS V-Rex, RANS Screamer
Bacchetta Giro A20, RANS V-Rex, RANS Screamer
#13
Biking Viking.
I look at what is suggested on the tire and go +10psi if I want to go fast and -10psi if I want a comfy ride.
#14
Senior Member
Mikey, 1.5" is 38 mm., 15% deflection would be 43.7 mm.
Looking at the charts for the first time it looks like I've used the tire deflection method for years without knowing it. Also from the chart in #10 you could drop to about 80 psi (unladen) so if I were you I'd experiment with that.
Brad
Looking at the charts for the first time it looks like I've used the tire deflection method for years without knowing it. Also from the chart in #10 you could drop to about 80 psi (unladen) so if I were you I'd experiment with that.
Brad
#15
the commutor / tourer
Thread Starter
Join Date: Aug 2004
Location: jacksonville fl
Posts: 626
Bikes: trek 6700 turned touring machine, giant TCR2
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 1 Time
in
1 Post
Wow! I am learing a lot on this thread. according to the spreadsheet linked in post number 7, if my tires are 38mm, the correct tire pressures would be 78 psi in the rear wheel and 39 psi in the front!
I don't think I can go that low in the front... I don't know what the minimum tire pressure is in that tire... and it doesn't say on the kenda website.
Wait... am I using that spreadsheet correctly? I put 38mm in tire size... 265lbs for total weight (bike, me, and gear)... and 65% on rear, 35% on front.
Results: 172 lbs on rear wheel, 93 lbs on front wheel.
Recomended PSI: Front 39psi Rear 78psi.
Does anyone know the lowest pressure I can put into these tires without running into pinch flats and the like?
I don't think I can go that low in the front... I don't know what the minimum tire pressure is in that tire... and it doesn't say on the kenda website.
Wait... am I using that spreadsheet correctly? I put 38mm in tire size... 265lbs for total weight (bike, me, and gear)... and 65% on rear, 35% on front.
Results: 172 lbs on rear wheel, 93 lbs on front wheel.
Recomended PSI: Front 39psi Rear 78psi.
Does anyone know the lowest pressure I can put into these tires without running into pinch flats and the like?
__________________
"Ready to retire, just can't afford it yet!"
"Ready to retire, just can't afford it yet!"
Last edited by mcavana; 01-12-12 at 01:06 PM.
#16
Banned
Does anyone know the lowest pressure I can put into these tires without running into pinch flats and the like?
When the black-ice conditions require studs I am riding at 2 bar, or about 30psi.
but the rate of speed is slow, then , and the rolling resistance larger, at lower PSI.
I cannot comment on you , your tires, and what conditions you will encounter.
that is for you to experiment with.
Different, wider tires have greater volume.. if you want to ride on the sand,
get as wide a tire as will fit. big apple 60mm perhaps.. Those are skinwall .
might ripple under hard acceleration like a top fuel dragster tires, then..
#17
working on my sandal tan
Join Date: Aug 2011
Location: CID
Posts: 22,620
Bikes: 1991 Bianchi Eros, 1964 Armstrong, 1988 Diamondback Ascent, 1988 Bianchi Premio, 1987 Bianchi Sport SX, 1980s Raleigh mixte (hers), All-City Space Horse (hers)
Mentioned: 98 Post(s)
Tagged: 0 Thread(s)
Quoted: 3868 Post(s)
Liked 2,559 Times
in
1,574 Posts
Wow! I am learing a lot on this thread. according to the spreadsheet linked in post number 7, if my tires are 38mm, the correct tire pressures would be 78 psi in the rear wheel and 39 psi in the front!
I don't think I can go that low in the front... I don't know what the minimum tire pressure is in that tire... and it doesn't say on the kenda website.
Wait... am I using that spreadsheet correctly? I put 38mm in tire size... 265lbs for total weight (bike, me, and gear)... and 65% on rear, 35% on front.
Results: 172 lbs on rear wheel, 93 lbs on front wheel.
Recomended PSI: Front 39psi Rear 78psi.
Does anyone know the lowest pressure I can put into these tires without running into pinch flats and the like?
I don't think I can go that low in the front... I don't know what the minimum tire pressure is in that tire... and it doesn't say on the kenda website.
Wait... am I using that spreadsheet correctly? I put 38mm in tire size... 265lbs for total weight (bike, me, and gear)... and 65% on rear, 35% on front.
Results: 172 lbs on rear wheel, 93 lbs on front wheel.
Recomended PSI: Front 39psi Rear 78psi.
Does anyone know the lowest pressure I can put into these tires without running into pinch flats and the like?
After running those tires at 100psi f/r , I think you'll find a lot more grip and comfort from running lower pressures. Keep an eye on your tire pressures, and if you do start having pinch flats, bump up the psi a little.
- Scott
#18
Certified Bike Brat
Join Date: Jan 2011
Location: Montreal, Quebec
Posts: 4,251
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 5 Post(s)
Likes: 0
Liked 6 Times
in
6 Posts
narrower rims are more likely to split open with fatter tires inflated to higher pressures.
schwalbe, for instance, recommends that you not inflate really fat tires to the max psi when using narrower rims than recommended for the tire.
conversely, that means wider rims are more likely to withstand such inflation pressures.
schwalbe, for instance, recommends that you not inflate really fat tires to the max psi when using narrower rims than recommended for the tire.
conversely, that means wider rims are more likely to withstand such inflation pressures.
Last edited by Burton; 01-12-12 at 09:19 PM.
#19
the commutor / tourer
Thread Starter
Join Date: Aug 2004
Location: jacksonville fl
Posts: 626
Bikes: trek 6700 turned touring machine, giant TCR2
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 1 Time
in
1 Post
Holy crap! Those of you that are riding at maximum PSI for no particular reason really need to try the formulas mentioned in this thread. I took my first 15 mile ride last night with the new pressures.... and the difference was unbelievable.
Before this thread I had both front and rear tires maxed out at 100psi. Last night I had 40psi in the front tire and 70psi in the rear. The ride was smooth as silk. The bike was much more stable, and it was rediculous how well the front tire was hooking up compared to the higher psi's. In fact I went to the same spot with the loose sand where I lost it before and kept circling over where I fell. At 40psi, that tire isn't slipping anywhere regardless of loose sand!!!
I didn't notice any increased resistance... in other words the bike didn't feel any slower. thank you to everyone that helped me on this. You guys rock.
Mikey
Before this thread I had both front and rear tires maxed out at 100psi. Last night I had 40psi in the front tire and 70psi in the rear. The ride was smooth as silk. The bike was much more stable, and it was rediculous how well the front tire was hooking up compared to the higher psi's. In fact I went to the same spot with the loose sand where I lost it before and kept circling over where I fell. At 40psi, that tire isn't slipping anywhere regardless of loose sand!!!
I didn't notice any increased resistance... in other words the bike didn't feel any slower. thank you to everyone that helped me on this. You guys rock.
Mikey
__________________
"Ready to retire, just can't afford it yet!"
"Ready to retire, just can't afford it yet!"
#20
The Left Coast, USA
No, no, no...stop obseessing on what the tire says and don't look at calculators.
I know your bike, I use a couple of those treks zx-s for commuting and touring. It's simple, back off the maximum pressure until you have a fair compromise between good rolling, firm ride, and a little bounce, suspension in the tires. It's a matter of taste, forget the numbers. It may work out to be a 15% sag, and maybe not.
At the top of the high pressure the tires will feel twichy and brittle, Too low and they feel slow, noodley and you may get pinch flats. Find the sweet spot, every rig and rider is different. For me, I'll guess I'm most often 10% below max pressure, but you get there by feel and not some stupid calculator or chart... the numbers are an afterthought.
I know your bike, I use a couple of those treks zx-s for commuting and touring. It's simple, back off the maximum pressure until you have a fair compromise between good rolling, firm ride, and a little bounce, suspension in the tires. It's a matter of taste, forget the numbers. It may work out to be a 15% sag, and maybe not.
At the top of the high pressure the tires will feel twichy and brittle, Too low and they feel slow, noodley and you may get pinch flats. Find the sweet spot, every rig and rider is different. For me, I'll guess I'm most often 10% below max pressure, but you get there by feel and not some stupid calculator or chart... the numbers are an afterthought.
#21
working on my sandal tan
Join Date: Aug 2011
Location: CID
Posts: 22,620
Bikes: 1991 Bianchi Eros, 1964 Armstrong, 1988 Diamondback Ascent, 1988 Bianchi Premio, 1987 Bianchi Sport SX, 1980s Raleigh mixte (hers), All-City Space Horse (hers)
Mentioned: 98 Post(s)
Tagged: 0 Thread(s)
Quoted: 3868 Post(s)
Liked 2,559 Times
in
1,574 Posts
Holy crap! Those of you that are riding at maximum PSI for no particular reason really need to try the formulas mentioned in this thread. I took my first 15 mile ride last night with the new pressures.... and the difference was unbelievable.
Before this thread I had both front and rear tires maxed out at 100psi. Last night I had 40psi in the front tire and 70psi in the rear. The ride was smooth as silk. The bike was much more stable, and it was rediculous how well the front tire was hooking up compared to the higher psi's. In fact I went to the same spot with the loose sand where I lost it before and kept circling over where I fell. At 40psi, that tire isn't slipping anywhere regardless of loose sand!!!
I didn't notice any increased resistance... in other words the bike didn't feel any slower. thank you to everyone that helped me on this. You guys rock.
Mikey
Before this thread I had both front and rear tires maxed out at 100psi. Last night I had 40psi in the front tire and 70psi in the rear. The ride was smooth as silk. The bike was much more stable, and it was rediculous how well the front tire was hooking up compared to the higher psi's. In fact I went to the same spot with the loose sand where I lost it before and kept circling over where I fell. At 40psi, that tire isn't slipping anywhere regardless of loose sand!!!
I didn't notice any increased resistance... in other words the bike didn't feel any slower. thank you to everyone that helped me on this. You guys rock.
Mikey
For the first couple of years, I was a little afraid to ride my road bike. It felt twitchy and not well connected to the ground, because I was naively inflating both tires to 100psi (and I'm a light guy). Part of that was inexperience, but bumping up the tire size and lowering the tire pressures really helped transform the bike into something I will hop onto with no hesitation.
- Scott
#22
Senior Member
Burton, there are tubeless tires for road. They have a dedicated rim/ tire setup.
Thread
Thread Starter
Forum
Replies
Last Post
ShortestStraw
General Cycling Discussion
13
10-25-13 04:09 AM
mikemartin
Bicycle Mechanics
21
10-30-12 09:51 AM