P-38 build

DIscuss anything relating to non-standard cycles and their equipment.
UpWrong
Posts: 2409
Joined: 31 May 2009, 12:16pm
Location: Portsmouth, Hampshire

Re: P-38 build

Post by UpWrong »

Two things: I've repaired the seat cover and secondly, I'm wondering if I was sent a smaller cover than I should have for the large frame.

I repaired it with strong nylon thread with the addition of some upholstery seat base webbing sandwiched between the seat mesh and the seat pocket material. For good measure I then applied super glue along the stitched seat webbing.

It looks to me like the seat pocket is not far enough on. The velcro is about 1.5 inches away from where it needs to be to fasten it, meaning the seat cover would need to be about 3 inches longer. Is it possible I was sent a medium size seat cover when my frame size is large?

As a result the seam of the cover is/was in a position where it is subjected to more tension and hence it pulled apart?
IMG_20220219_114135.jpg
IMG_20220219_122556_HDR.jpg
IMG_20220219_122628_HDR.jpg
UpWrong
Posts: 2409
Joined: 31 May 2009, 12:16pm
Location: Portsmouth, Hampshire

Re: P-38 build

Post by UpWrong »

No reply from Lightning Bikes. I came across a photo of another large P-38 which looked to have an equally short and damaged seat cover. My wife suggested I do up the velcro fastening on the seat pocket at the front before lacing down the sides of the seat. Did that. It looked OK but as soon as I tried to ride it, the velcro came undone and the seat sagged.

I'll tighten the lacing, ride it and see if the restitched seam holds. If not, I'll perform some more drastic surgery, Namely, remove the seat pocket and seat pad sleeve, shorten the mesh back to the apex of the seat back and seat base, use some seat base strapping to create a new seat base hammock, obtain a seat pad to attach on top of the seat base hammock.
UpWrong
Posts: 2409
Joined: 31 May 2009, 12:16pm
Location: Portsmouth, Hampshire

Re: P-38 build

Post by UpWrong »

The seat survived a one hour ride yesterday. It had sagged a bit by the end of the ride but I was expecting that the lacing would need retensioning after a first ride. In the end I decided to change the lacing a bit rather than just retension it in order to hold the front seat cover pocket better on the seat frame. Will aim for a longer ride tomorrow.

I'm inclined to think now that the original thread and stitching of the front seam was simply not up to the job. I'll order a new cover whenever I should need it, but add another line of stitching to the seam with a stronger thread.

Other things ... I bought a frame pump to fit. Also I'm planning to remove the short section of chain tube and just put a little helicopter tape on the nearest point of the frame as a precaution. I don't think it will touch with a properly sized chain. And when I do that I have a lighter FD to put on, a vintage Deore bought on this forum. It's about 50g lighter than the Altus. And I will change the front tyre from a Kojak to a Maxxis 120tpi folding DTH. I've seen yet another measurement of the high rolling resistance of Kojaks, this one from Trisled.
UpWrong
Posts: 2409
Joined: 31 May 2009, 12:16pm
Location: Portsmouth, Hampshire

Re: P-38 build

Post by UpWrong »

The seat cover seam held up on a slightly longer ride today. I noticed myself tending to slide forward off the seat so I have this evening tilted the seat back a little to about mid-point on its range of setting. This will also open the hip angle. The downside is that it's a bit harder to reach the ground.

I found the ride somewhat rough today. A lot of road surface were in bad condition. I wonder if I could squeeze a 30mm Schwalbe One under the mudguard.

Disappointingly, no Strava achievements today. But there was a harsh wind to battle against.
UpWrong
Posts: 2409
Joined: 31 May 2009, 12:16pm
Location: Portsmouth, Hampshire

Re: P-38 build

Post by UpWrong »

I changed the front tyre to a folding Maxxis DTH. Also gave the chain a wipe and then lubed with Finish Line dry. I want to avoid chain tattoos. My usual lube is Finish Line wet, so this is new for me. I went for quite a hard ride in the cold wind: 15 miles and 865ft of climbing. i got a few personal Strava records this time. I noticed the change in weight distribution having shortened the seat says by 1cm+ to lay the seat back a bit more.

The 9-speed Shimano gear change was a repeated irritant. The up shift is fine but the down shift usually required a second push by the thumb to get it into gear. I thought I'd mastered it with a slight overshift and hold whilst it changed but that didn't work reliably today. The SRAM X series with its 1:1 actuation ratio is far superior. I might look at doing a swap with the Azub trike - which is up for sale by the way in the "for sale" section if you haven't already seen it.

The 28mm Durano is a bit harsh so I've ordered a 28mm race tyre which should be faster and more comfortable and more susceptile to fairy visits unfortunately. I still need to remove the chain tube and change the FD for a lighter one.
Blondie
Posts: 239
Joined: 23 May 2021, 5:11pm

Re: P-38 build

Post by Blondie »

What’s your weight and what pressures are you running on the 28mm tyres? I have a 32mm on rear and run at 60 psi, I weigh 75kg at moment. Runs pretty smooth.
UpWrong
Posts: 2409
Joined: 31 May 2009, 12:16pm
Location: Portsmouth, Hampshire

Re: P-38 build

Post by UpWrong »

Snap! 75Kg at the moment. I had the 28mm Durano inflated to 80psi and the 38mm DTH inflated to just shy of 60 psi. The 32mm Pasela on my Paseo usually gets inflated to 70psi, but that has suspension.
UpWrong
Posts: 2409
Joined: 31 May 2009, 12:16pm
Location: Portsmouth, Hampshire

Re: P-38 build

Post by UpWrong »

I had a pair of 28mm Schwalbe One V-guard evolution tyres arrive today. According to Bicycle Rolling Resistance, almost identical to GP4000S II in rolling resistance with significatly better puncture resistance. It's a shame Schwalbe don't make them anymore. In my hand, 30mm tread width and 60mm total width excluding folding beads.Min pressure 85 psi, but I shall run them at 80 psi.

My control of the P-38 is improving, and with it my confidence in traffic. I tried to measure the seat back angle today, always an arbitrary value.The seat may be at 55 degrees above horizontal but I reckon I'm riding at 50 degrees since my coccyx is away from the seat back.Whilst it's the best climbing bent I've ridden, air drag is slowing me down above 15 mph in comparison to the Paseo I think with its seat at 38 degrees.
UpWrong
Posts: 2409
Joined: 31 May 2009, 12:16pm
Location: Portsmouth, Hampshire

Finished !!

Post by UpWrong »

It's done. All changes made. Some photos in the "pictures of my bent" thread. Ready to ride weight as shown 29 lbs which I think is impressive given all the accessories fitted.
IMG_20220311_161918_HDR.jpg
Schwalbe One V-guard tyre fitted, new FD fitted, chain-tube removed.
The DT-Swiss disc rim makes tyre changing extremely difficult. I said finished but maybe I'll build a new back wheel. I have a Mavic Open Sport rim I could use. It took me over an hour to change the tyre on the DT-Swiss. Hard to get the Durano off, hard to get the One on.

EDIT: The tyre when mounted had a width of 28mm and a height of 27mm.
Blondie
Posts: 239
Joined: 23 May 2021, 5:11pm

Re: P-38 build

Post by Blondie »

Same seat bag colour as me
yostumpy
Posts: 994
Joined: 29 Oct 2010, 6:56pm

Re: P-38 build

Post by yostumpy »

Racing at Colchester on April 2nd?
UpWrong
Posts: 2409
Joined: 31 May 2009, 12:16pm
Location: Portsmouth, Hampshire

Re: P-38 build

Post by UpWrong »

yostumpy wrote: 24 Mar 2022, 10:12pm Racing at Colchester on April 2nd?
I shall be there, but not with the P-38. It doesn't have a chainring guard and I haven't tried getting it in the car yet. It's more of an allrounder than a speed machine anyway. The seat is not laid back enough.
UpWrong
Posts: 2409
Joined: 31 May 2009, 12:16pm
Location: Portsmouth, Hampshire

Re: P-38 build

Post by UpWrong »

I'm planning some updates. One is a change form Shimano 9-speed to SRAM 9-speed RD and shifter to improve the shifting. Another is a switch to a wheel with a Mavic Open Sport rim on a Deore rear hub. It's too hard changing a tyre with the DT460.

Also I'm readying a different chainset with chain guard so I can enter it into the BHPC race in Stockport next month.
UpWrong
Posts: 2409
Joined: 31 May 2009, 12:16pm
Location: Portsmouth, Hampshire

Re: P-38 build

Post by UpWrong »

Got the SRAM RD and shifter on it. Vastly superior to Shimano. Did a ride with the rear Schwalbe One at 70 psi and the front Maxxis DTH at 50 psi. I've ordered some spokes from Spa to build a rear wheel. The disk hub and Mavic rim will be cannibalised from other wheels not in use.

EDIT: oh yes, and the restitched seat cover seems to be holding up.
UpWrong
Posts: 2409
Joined: 31 May 2009, 12:16pm
Location: Portsmouth, Hampshire

Re: P-38 build

Post by UpWrong »

The riding position is feeling a bit too closed. I guess the choice is to stick with it and adapt, or switch to shorter cranks. Current cranks are 160mm, I'm more used to 150mm on a SWB. Will I notice the effect of 10 mm on hip angle? Will I need to lower the gearing to compensate for less leverage?
Post Reply