DNM burner rcp-2s spring

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j bjork   10 kW

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DNM burner rcp-2s spring

Post by j bjork » Jun 14 2019 2:12pm

I have one of these on my bike, with the standard 550lbs spring.
The bike is about 60kg, and I am almost 90kg.
The bike is one of those dirtbike look alikes, and i mostly drive it on forest trails.
Here is the build thread: https://endless-sphere.com/forums/viewt ... =6&t=98723

I have to set hard preload to get it in the right ridehight, and it bottoms out easy. So I want a stiffer spring.
I think I have seen those with 750lbs springs, but I have´nt found those springs now.

Does anyone here know where I can find a suitible spring?

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MadRhino   100 GW

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Re: DNM burner rcp-2s spring

Post by MadRhino » Jun 14 2019 8:32pm

There is a number punched on the spring. Ex.: .550 2.75

The first number is spring weight (lbs required to compress one inch), the second is the travel.

Once you know the spring weight and travel that you need, you can buy the spring used or new, steel or titanium. I would first check for used ones on Pinkbike, or new at Chain Reaction Cycles.
Make it fool-proof, and I will make a better fool.
Current bikes
Street:
Trek Session 10 mod. Variable geometry. 70mph
Dirt:
Santa Cruz V10. 50mph

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brumbrum   100 kW

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Re: DNM burner rcp-2s spring

Post by brumbrum » Jun 15 2019 2:53am

MadRhino wrote:
Jun 14 2019 8:32pm
There is a number punched on the spring. Ex.: .550 2.75

The first number is spring weight (lbs required to compress one inch), the second is the travel.

Once you know the spring weight and travel that you need, you can buy the spring used or new, steel or titanium. I would first check for used ones on Pinkbike, or new at Chain Reaction Cycles.
You may be able to find a dnm 650 or even 750lb spring if lucky, otherwise, from memory i believe the dnm spring is an unusual internal diameter compared to the leading market springs so it might be difficult getting a 3rd party replacement. Try and measure and see what you can find
My NYX and cromotor build
viewtopic.php?f=6&t=74615
My LMX 161 dirt bike build
viewtopic.php?f=6&t=94074

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Overclocker   10 kW

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Re: DNM burner rcp-2s spring

Post by Overclocker » Jun 15 2019 7:25am

was on the same boat. 550 was too soft

em3ev used to sell springs but not anymore

you could also contact DNM in taiwan to get spare springs

i ended up getting a slightly longer RCP-3 w/ 650lb spring

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Re: DNM burner rcp-2s spring

Post by j bjork » Jun 15 2019 8:06am

Thanks guys, the spring does´nt have the travel marked on it from what I have seen.
But the travel on the shock should be 56mm or 2.2"

I did some mesurements on the spring and shock with everything still mounted on the bike.
It seems like the maximum lenght of the spring could be 135mm, but then it would probably be difficult to mount. So I think 5" or 127mm is about right. Maby slightly less.

The outer diameter is about 53mm, and the thickness of the spring is 8,5mm. So the inner diameter should be about 36mm or 1.42", I think 1.4" sounds about right.

I would like to find something in EU to avoid import charges, but it is not critical.
I have looked at some sites, and the most springs did´nt have mesurements. Only what shocks they were intended for. And they were for the most part not stiffer then what I already have.

I haven´t found much of anything on DNM:s webb page, but I haven´t wrote to them asked so far.

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Re: DNM burner rcp-2s spring

Post by brumbrum » Jun 15 2019 8:42am

Taken from Ti-Springs website "36.5mm ID Fitment - For Use With DVO Suspension, Cane Creek, BOS Suspension, Ohlins, Marzocchi, Manitou Shocks & X-Fusion Shocks" So springs made by those companies should fit

35mm and 38mm are also other standard sizes
My NYX and cromotor build
viewtopic.php?f=6&t=74615
My LMX 161 dirt bike build
viewtopic.php?f=6&t=94074

j bjork   10 kW

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Re: DNM burner rcp-2s spring

Post by j bjork » Jun 16 2019 6:37am

Thanks, I took off the spring to check.
It is 130mm long, and 36mm id. The plates it stands on (I dont know the name in English) are 35mm where they fit in the sping. But i guess 36.5mm is closest, 35mm would be very tight.

Image

I also measured the stroke on the wheel and spring. Those 56mm might be possible without the rubber stopper, it is 44mm before it hits the rubber.
With a slight compression of the rubber, about 45mm stroke on the shock I get about 160mm travel on the rear wheel.

Image

This is how I mesured travel.

I tried the calculator on ti springs site, they just want travel and rider weight. Nothing about bike weight.
I figured my bike is a lot heavier then a downhill bike, and added some weight.
With 280lbs I get a spring of about 1350lbs :shock:

Already with 200lbs I get a spring of about 1000lbs, and I think that is about what I weight..

I don´t know if something is seriously wrong with my measurements, or if all bike stuff is made for 40-50kg people :?

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Re: DNM burner rcp-2s spring

Post by rzrsharp519 » Jul 25 2019 8:46am

I just bought a DNM RCP-2S spring as well, for the same style bike. I’m still waiting on components so I haven’t sat on it yet. I weigh 150lbs (68kg). Do you think the 550lbs spring will be suitable? And did you ever find a replacement spring? Thanks!

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Re: DNM burner rcp-2s spring

Post by j bjork » Jul 25 2019 2:19pm

I was able to buy a 750lbs spring from dnm, they did´nt have stiffer than that.
It is better, but stiffer would have been better for me at least.
For you 750lbs would probably be ok, but I think 550 will be too soft.
I weight abut 90kg.
On the road 550lbs will probably be fine, but on trails in the woods I think it will be way too soft for you too.

The spring was not expensive, but shipping was something like $70. I bought 2, so I could sell one if you live in eu.

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Re: DNM burner rcp-2s spring

Post by rzrsharp519 » Jul 25 2019 2:31pm

You’re probably right, the 550lbs won’t do. I’m thinking I’d be good with the 650lbs, EM3ev only suggests the 750lbs for riders who weigh over 200lbs. I don’t want it to be too stiff, as I only weigh 150lbs (a bit less actually). Where did you find a spring that fit? I’m in Canada. Since I bought the shock on Amazon Prime I have some time to return it if I can’t find a better spring. Thanks for the help!

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Re: DNM burner rcp-2s spring

Post by j bjork » Jul 25 2019 3:04pm

Did they really counted the wight of the bike when they suggested the 750lbs spring only for heavier riders?
I got mine from dnm in Taiwan.
You can always try with the 550lbs spring first.

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Re: DNM burner rcp-2s spring

Post by rzrsharp519 » Jul 26 2019 5:25am

EM3ev is a reputable company and I’d assume they know what they’re talking about, so yes I think they took the weight of the bike into consideration. They sell DNM RCP-3 750lbs replacement springs...I’ll ask them if it fits the RCP-2S, and if they don’t know, I’ll just add it to my next order and see for myself. It’s only $13CAD. And ya I would try riding with the 550lbs, but my rims aren’t here yet so like I said, I sadly haven’t been able to sit on the bike yet. Thanks for the info!

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Re: DNM burner rcp-2s spring

Post by rzrsharp519 » Aug 09 2019 11:03am

My solution:

I was able to purchase a 750LBS spring for $13CAD from EM3ev and didn’t have to pay much more for shipping because it was added to an already very large order. The site says the spring is for the RCP-3, but it fit my RCP-2S perfectly. The only difference is the thickness of the spring, all other dimensions are the same.

If you only order the spring, it comes to $41.38CAD after shipping (to Canada).

I would say this is the best solution if you want to upgrade the RCP-2S from 550LBS to 750LBS. Also, a local bike shop also told me they could get a Fox spring which would probably fit for $70.

I’m still waiting on my moto rims to arrive so I haven’t tried it on my my EEB build yet. Hopefully it will be sufficient and the settings will work properly even though the spring wasn’t intended for this shock.

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Re: DNM burner rcp-2s spring

Post by ekwek » Jan 28 2020 1:28pm

Hey everybody,
Vectorebike.com is offering damper with 850lbs spring. Already got it

https://vectorebike.com/suspension/rcp-2

Greetings from Austria,
Rene

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Re: DNM burner rcp-2s spring

Post by synics » May 05 2020 10:10pm

ekwek wrote:
Jan 28 2020 1:28pm
Hey everybody,
Vectorebike.com is offering damper with 850lbs spring. Already got it

https://vectorebike.com/suspension/rcp-2

Greetings from Austria,
Rene
Did it make a difference? Do you have a heavy hub motor? I was thinking of fabricating a higher bracket on my frame so that I can mount a full moto shock on mine with at least a 1000lb spring. I will have a QS273 motor and I weight 200lbs...

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Re: DNM burner rcp-2s spring

Post by Jonno » May 06 2020 1:28am

Like this?

A 1000lb pit bike shock 280mm - much better :)
https://www.ebay.co.uk/itm/Pit-Bike-Rea ... 2749.l2649
IMG_20200506_065405a.jpg
IMG_20200506_065405a.jpg (55.35 KiB) Viewed 346 times

Note to self - clean bike!
Modified EEB frame, 888 forks, 280mm stiffer rear shock, QS273 40h V3 , Nucular Electronics 24F controller, 92V @ 36ah 26650 cells, 300a BMS, Hope V4 + Variable regen braking

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Re: DNM burner rcp-2s spring

Post by Jonno » May 06 2020 2:42am

Ok so I've just looked in my junk box in found 3 x DNM springs

2 x 650lb/in
1 x 750lb/in

Will send to 3 lucky riders for postage cost :bigthumb:

Anybody need one?



PM me :D

Jonno
Modified EEB frame, 888 forks, 280mm stiffer rear shock, QS273 40h V3 , Nucular Electronics 24F controller, 92V @ 36ah 26650 cells, 300a BMS, Hope V4 + Variable regen braking

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Re: DNM burner rcp-2s spring

Post by synics » May 06 2020 8:40am

Jonno wrote:
May 06 2020 1:28am
Like this?

A 1000lb pit bike shock 280mm - much better :)
https://www.ebay.co.uk/itm/Pit-Bike-Rea ... 2749.l2649

IMG_20200506_065405a.jpg


Note to self - clean bike!
Yes that's exactly what I'm talking about! Do you know what kind of travel that thing has? Both stroke and then at the wheel? Have you jumped with it?

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Re: DNM burner rcp-2s spring

Post by Jonno » May 06 2020 9:14am

I'll measure it later -as I have a need for a ride :bigthumb:
Modified EEB frame, 888 forks, 280mm stiffer rear shock, QS273 40h V3 , Nucular Electronics 24F controller, 92V @ 36ah 26650 cells, 300a BMS, Hope V4 + Variable regen braking

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MadRhino   100 GW

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Re: DNM burner rcp-2s spring

Post by MadRhino » May 06 2020 12:51pm

Just for info about suspension tuning.

With a heavier wheel, a bigger, longer shock might be required for proper rebound control of unsuspended weight (the wheel). The damper valve may need mod, or thicker oil used, in order to tame the rebound oscillation of a heavy wheel, to prevent the wheel bouncing off the ground, and so that suspension can be quickly ready to absorb the next hit.

A harder spring is required for a heavier suspended weight (bike and rider, not wheel).
The proper spring weight rating is the one that can be tuned to 40% suspension travel sag with rider on the bike, while being compressed no less than a third, and no more than half of the shock travel.

This should clear the myth that a harder spring is required for a heavier wheel, when in fact it is a better rebound control tuning range that is required.
Last edited by MadRhino on May 06 2020 1:01pm, edited 1 time in total.
Make it fool-proof, and I will make a better fool.
Current bikes
Street:
Trek Session 10 mod. Variable geometry. 70mph
Dirt:
Santa Cruz V10. 50mph

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Re: DNM burner rcp-2s spring

Post by synics » May 06 2020 12:59pm

MadRhino wrote:
May 06 2020 12:51pm
Just for info about suspension tuning.

With a heavier wheel, a bigger, longer shock might be required for proper rebound control of unsuspended weight (the wheel). The damper valve may need mod, or thicker oil used, in order to tame the rebound oscillation of a heavy wheel, to prevent the wheel bouncing off the ground, and so that suspension can be quickly ready to absorb the next hit.

A harder spring is required for a heavier suspended weight (bike and rider, not wheel).
The proper spring weight rating is the one that can be tuned to 40% suspension travel sag with rider on the bike, while being compressed no less than a third, and no more than half of the shock travel.
I agree! Do you have any specific recommendations on shocks besides the DNM MTG-RC? I was looking at some used WP shocks off KTM 85s, or like a 110 dirtbike...they're pretty big though, like 14" I'm going to fabricate a new shock mount around the shock so I want to get it right.

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MadRhino   100 GW

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Re: DNM burner rcp-2s spring

Post by MadRhino » May 06 2020 1:07pm

Check for shocks that were on motorcycles with heavy rear wheel. That is your best chance to have enough rebound control so that it won’t need mod. Then shop for a spring to tune your riding weight.
Make it fool-proof, and I will make a better fool.
Current bikes
Street:
Trek Session 10 mod. Variable geometry. 70mph
Dirt:
Santa Cruz V10. 50mph

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MadRhino   100 GW

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Re: DNM burner rcp-2s spring

Post by MadRhino » May 06 2020 1:16pm

Dirt bikes typically don’t have heavy wheel. Alloy rim, narrow tires. You are looking for a bike that has wide tire and heavy rim. The shock may not be long, just big with more oil capacity.
Make it fool-proof, and I will make a better fool.
Current bikes
Street:
Trek Session 10 mod. Variable geometry. 70mph
Dirt:
Santa Cruz V10. 50mph

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Re: DNM burner rcp-2s spring

Post by synics » May 06 2020 6:34pm

MadRhino wrote:
May 06 2020 1:16pm
Dirt bikes typically don’t have heavy wheel. Alloy rim, narrow tires. You are looking for a bike that has wide tire and heavy rim. The shock may not be long, just big with more oil capacity.
Dirt bikes have super wide rear tires, lol. My KTM has an almost 6" wide back tire. Heavy as hell. Although no, not as heavy as a QS273. I'm probably just going to get a 11.5" DNM moto shock with a 1000lb spring as a cheap option to start with.

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Re: DNM burner rcp-2s spring

Post by MadRhino » May 06 2020 7:33pm

synics wrote:
May 06 2020 6:34pm
MadRhino wrote:
May 06 2020 1:16pm
Dirt bikes typically don’t have heavy wheel. Alloy rim, narrow tires. You are looking for a bike that has wide tire and heavy rim. The shock may not be long, just big with more oil capacity.
Dirt bikes have super wide rear tires, lol. My KTM has an almost 6" wide back tire. Heavy as hell. Although no, not as heavy as a QS273. I'm probably just going to get a 11.5" DNM moto shock with a 1000lb spring as a cheap option to start with.
It will make your wheel bounce even more, if the spring is too hard for your riding weight. Just replace the oil in the shock with thicker grade, not perfect but better result and cheap.

Real dirt bikes are typically on 2.75 front, 4.0 rear. On 6.0, your KTM is a Dual Sport. Still, since it is made for off road handling, some serious effort must have been made to keep the wheel light. Heavy motorcycle wheels are on big touring bikes.
Make it fool-proof, and I will make a better fool.
Current bikes
Street:
Trek Session 10 mod. Variable geometry. 70mph
Dirt:
Santa Cruz V10. 50mph

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