tiger1964 

OK, I decided to try something more "modern" and decided to replace the 23mm Vredstein Fortezza tires (running at 145psi) with a set of Continental 4000S in 28mm (to run at 115PSI, apparently the max) after reading on-line about lowered rolling resistance. Installed them and also decided on Vittoria latex tubes. Installed them and the bike sat for over a week due to being sick (still am, actually). Went for a ride finally on Wednesday. These seemed to be at least as fast as what I took off, subjectively, and I can get used to not having the boneshaker ride, I guess. Well, 10 miles into an 18 mile ride, lost air in the front tire. Swapping in a spare (butyl) tube, could not locate the hole but I installed anyway and made it home. Looking closer at the holed tube, it looks like a spoke-head 'nick', I could not find the offending spoke but the rim strips seem to be original equipment, 1980 vintage. Went to the LBS and bought "plastic" replacement rim bands, and am cleaning up the rims to install -- stalling because the spoke ends and nipples are recessed enough that I need a small Dremel bit to grind anything down, so off to Big Orange I'll go before proceeding further.

Meanwhile, a question. I've been reading about Presta tubes with removable cores to install sealant "goop". Of course, right now, that sounds interesting. Looking closely at the Presta valve, right below the usual loosen-to-inflate-knurled knob, the uppermost part of the rest of the valve is a silver color and might have faint "flats" where the rest of the valve (51mm) is smooth brass with no threads. Is this where the core removes and, if so, what kind of tool? Should I install "goop"?

BTW, these tires really look fat, and I read on-line that the 28's are in truth even wider than that, they clear the chain stays but not by a huge amount, perhaps I should have bought 25's.

mercator

You really run 145psi? Do you mind if I ask what you weigh?

squirtdad

nice is the park tool..... but my tufo sealant for tubulars came with a little plastic job...... I can say to let the pressure out first....I am still looking for my part tool in the garage after not doing so
,

scozim 

That's the first thing that struck me too except for the weight thing. I normally run at 120 psi and only went higher with some tubulars in a hill climb race

tiger1964 

Thanks for the input!

150PSI indicated on my Park pump seems to work out to 145PSI on my digital gauge, so, yeah. Weight? I retired at 209LB, currently 184.2LB, won't relent until I am at least in the upper 160's.

Hence the user name "squirtdad"? I can imagine that qualifies and "hardest lessons, best learned"

HTupolev

If I were you, I'd ride those 28s considerably softer than 115PSI. Maybe somewhere in the 85-100 range for the rear tire.

davester

Ditto. You weigh the same as I do. By pretty much any tire pressure guideline out there you are way over the recommended pressure for your weight and tire width. You're losing out on the advantages (comfort, lowered rolling resistance, cornering grip) of running a wider tire by overinflating. I'd suggest something like 90 rear/75 front.

Also, overinflating the tire will make the tire fatter.

masi61

tiger1964 

Any thought on the tube cores?

Interesting, although this website https://www.bicyclerollingresistance...0s-ii-23-25-28 shows a steady decline in rolling resistance with increasing PSI. This is what drove me to change tire brands in the first place.

Shoot! Might need to drive 1 hour round trip to the LBS to exchange the strips -- I was given a choice and chose the plastic over tape. Was told basically no difference. You know, on my rims, the spoke tips and the heads of the nipples are recessed pretty far below the level of where the rim strip resides -- you'd think I wouldn't be having any issues at all.

I was topping off the old tires before every ride anyway, I've just noticed it's a few more pumps with the new ones, I figure between the latex tubes and the fact that the fat tires have more cc's of space in them anyway...

rm -rf

"The 28s seem really fat". I've never had 28s, but most reports on BF say they are wider, maybe 30 or even 32mm. But some have measured them as close to 28mm. Wider rims will let the tires be wider.
Search google: site:bikeforums.net GP4000 28 measured actual width

"...at 115 psi..."
Wow, that's way too high pressure.
Unless your roads are extremely smooth, very high pressures aren't faster, the bumps and vibrations use up energy, too. Let the tire sidewalls flex over rough roads, it'll be way more comfortable and at least as fast.

Try lowering the pressure 10 psi per ride -- it will take a few rides to get used to it. It'll likely feel weird at first.
Davester is right, try 75 psi front, 90 psi rear! (perhaps even a little lower.)

I'm at 170 pounds, and have very wide rims, so the 25mm GP4000S measure 29mm.
I use 65 psi front, 80 psi rear. For smooth roads and a very fast paced group ride, I'll go about 70 psi front, 85 psi rear. It might be marginally faster.
That's about 15% less pressure on the front, which is correct for a 45% front - 55% rear weight distribution.

Even on 23mm on standard width rims, I used 105-110 psi rear, 95-100 psi front, and probably could have lowered it.

~~~~

The big advantage of tires like the GP4000S are the overall lower rolling resistance (and better grip, too), compared to stiffer, puncture resistant tires. These good tires are still fast at reasonable pressures.

The chart shows the 28mm at:
120 psi: 11.6 watts
100 psi: 12.0 watts
080 psi: 12.7 watts

Just one watt higher at 80 psi.

63rickert

Some still unanswered questions here. Valve cores are not hard to remove. Needle nose pliers are fine. It would take a while to name the improvised tools that work. Sealant in clincher innertubes is not standard practice, but interesting enough to experiment with. If you want to give it a try, Orange Seal does not dry out for years.

The less clearance you have from tire to frame the more likely you are to have problems. Question is how bad you want the fat tires and how much would you risk for that. Jan Heine says 3mm is enough, my bikes I don't use less than 5mm, the 50s and 60s bikes I ride would have had more like 10mm as original. Others would see 10mm clearance as just an opportunity to stuff in some big tires.

Conti GP4000 iiS in 28mm nominal size will be in the range of 31mm wide when inflated on the current standard 23mm rims. On older standard 20mm rims the tires are more like 29mm wide. But there are enough other factors that you don't know unless you measure. At 31mm wide and your weight 60-70psi would be enough. At 29mm 70-80psi. They are very good tires and will tolerate a wide range of inflation pressures without ill effect. You will not experience sudden catastrophic loss of braking traction. You will wear the tires out faster. The rims are overstressed.

The bicyclerollingresistance website puts tires through a fixed protocol and tests lots of pressures no one would ever use. The drum tests only test what they test. Real world performance is different.

You lost 25 pounds? Wish I could. Congratulations.

63rickert

One more. Don't travel to LBS just to change rim strips. Lots of things work. For the past 30 years my wheels mostly get fibered strapping tape. There are plastic strips with a sharp edge and plastic strips that never cause problems. If using latex tubes this little stuff might matter. Or it might not.

rm -rf

Latex tubes
I've considered using latex, but decided against them. They seem just too fragile, and lose air fast, too. I think they'd only save a couple of watts. (The rolling resistance tests show these tires at around 10-15 watts per tire, how much lower could it go by switching tubes to latex?)

Instead, I use the "ultralight" tubes, which are in the 80 grams range instead of around 100 grams. I expect these thinner tubes will be a bit more comfortable, too.
The rolled up spare tube in my saddle bag takes up less space, too!

masi61

Maybe you could share what brand of plastic rim tape they sold you.

We're mostly postulating that the sharp edges of the the plastic rim tape contributed to the latex inner tube puncture but there are other possibilities to rule out as well.

1) It could have been a minor pinch under the tire bead during installation. It is especially important with latex tubes to go all the way around once installed with just slight pressure, pressing in the sidewalls all 360 degrees of rotation (valve stem until valve stem comes around again) and if you visualized any pink colored inner tube under the bead, let some air out and manipulate the bead until it is no longer visible. Using talc or baby powder during installation helps for some (I use Rema Tiptop talc and like it). Others say talc is unnecessary.

2) check the tire and rim for any burrs or sharp protrusions. Sometimes butyl tubes will go along fine when there is a shard of glass partly penetrating the tire casing. The same small protrusion could be enough to create a puncture.

tiger1964 

I'm willing to try that, except I've only been able to get off the toilet once in the past ten days long enough to ride -- I've found a malady that causes me to lose weight faster than the cycling does. Anyway, already was willing to get outside my comfort zone of the 145PSI pizza-cutters to try these. I'll attempt a baseline and then see what inflation results in best performance. Most of my time is on paved trails, I'm not really "bouncing", the rock-hard tires were already working OK.

I might try the Park PC1 tool and Orange Seal. Who knows? As for clearance, I'll admit the rear wheel was a wee bit out of true, I spent some time on it and it looks better now, hopefully the tire won't drag on the chain stays not the rim on the rear brake. Hopefully, at 25LB lost, I have not hit a "wall" and I continue to lose weight, especially once I get away from flatlander riding and hit real hills.

Guess what I found as a rear rim tape on this bike? Strapping tape. Ugh, a mess to get off, either the previous owner did that, or I did 20 years ago when I bought the bike, I cannot remember. The LBS gladly exchanged the plastic strips for tape, time to go install it.

Fair enough, but mere seconds on a one-hour ride is proving to be a good motivator, or otherwise I'd simply ride a 1950's newsboy bike.

This is what drove me to exchange the rim strips. Plus, I spent a chunk of time trying to ensure I did not have any pinches -- think I did OK there.

davester

Unfortunately, the testing protocol on that website measures only one of the two main components of rolling resistance. It measures the component that results from tire deformation, which consistently decreases with higher pressures. There's been a ton of work in the last decade or so on the other main component, which is the energy lost to vibration (i.e. lifting of the bike up and down over road irregularities. Even over relatively smooth roads this component is significant and increases with higher pressures, which is why racers have been switching to wider tires and lower pressures than were used ten years ago.

63rickert

Not so much switching to wider and lower than ten years ago as reverting to what was used 50 or more years ago. Skinny and hard was a blind alley that lasted too long.

tiger1964 

Any of that info available on-line?

Regardless, feeling well enough now to at least work on the bike a bit. The replacement rim tape is Velox brand, 16mm width. Alas, my rims (Super Champion "Gentleman") really did not want to accommodate the width, so I've been narrowing the tape to about 9mm with scissors... very tedious. About to remount the tires and if the weather clears tomorrow, venture out again. Wish me luck. Once I establish a baseline, I'll try lower pressures; as I still have a faint memory of the 70PSI Michelins on my 1971 Gitane, which felt like pedaling through pudding, this should be interesting.

tiger1964 

Did my usual 18.06 miles today; elapsed time just a whicker of my usual at 1h 1m 5s. As that's only my 2nd ride in two weeks and I presume I'm still weak, I guess OK; not enough to establish a baseline, perhaps average of 3 rides? Then maybe I'll try, eh, 105PSI.

On my Q in post #1 , right now on one latex tube w/removable core and one butyl w/out, so I cannot try goop even if I had some and the tool. Something to try later.

veganbikes

Dude that is crazy PSI! I am quite a bit heavier than you and run my 28s max at 90 PSI and frequently a little lower. I wouldn't load up with any goop or sealant just lower your pressure a bit and you will probably be in better shape. Extreme high pressures like that is for pro riders with a team car or neutral service tailing behind or in front. They also are happy to punish themselves day in and day out for glory, we don't have to do that.