Got Any DH Questions? Ask Them Here

PB Forum :: Downhill
Got Any DH Questions? Ask Them Here
Author Message
flag ajax-ripper
Posted: Dec 14, 2019 at 0:01 Quote
Whitelinerz wrote:
Last night I bought a 2017 identiti Mogul DH bike, it has a 7.5" rockshox vivid rear coil shock, I'm a bit heavy for this spring and I'm sitting around 50-60% sag lol.. As it isn't air, I'm gonna need a more harder spring. Please can someone help me with understanding spring sizes and lbs etc please?

For example 300x8.5, 8.5"x2.5" etc etc.. I just do not understand this lol

My spring currently is marked with (300X2.75)
Please if someone can guide me on getting the right spring for this shock, that'd be absolutely great! (I'm about 14 stone / about 90kg in weight)

Thanks in advance!

Here's the coles notes:
*Spring rate is the force (in lbs) required to compress a spring 1 inch. Example: a 450 lb/in spring will require 450 lb to compress it one inch, 900 lb to compress it 2 inches, 1350 lb to compress it 3 inches. The higher this number the stiffer the spring.
*The second number shown oin a spring is its stroke this is how far it can be compressed before binding. This nuymber must be matched to your shock. If you have a 3" stroke on your shock then you must have a 3" stroke spring.

There are a number of spring rate calculators available online that you can use to guestimate what spring rate you need for your bike.
flag spaceofades
O+
Posted: Dec 14, 2019 at 0:03 Quote
Whitelinerz wrote:
Last night I bought a 2017 identiti Mogul DH bike, it has a 7.5" rockshox vivid rear coil shock, I'm a bit heavy for this spring and I'm sitting around 50-60% sag lol.. As it isn't air, I'm gonna need a more harder spring. Please can someone help me with understanding spring sizes and lbs etc please?

For example 300x8.5, 8.5"x2.5" etc etc.. I just do not understand this lol

My spring currently is marked with (300X2.75)
Please if someone can guide me on getting the right spring for this shock, that'd be absolutely great! (I'm about 14 stone / about 90kg in weight)

Thanks in advance!
8.5x2.5 is the eye to eye (length) and shock stroke (shaft travel) of your shock. This is important to know if you're upgrading or swapping out your shock in the future, you'll want the numbers there to match.

For the spring, 300 identifies 300 pounds of force required to compress 1 inch of spring. The 2.75 is the stroke of the spring. It is important that the stroke of the spring is at the very least equal to, if not greater than the stroke of the shock. If it is less, the coils will bind and you will have problems.

I'd recommend for you to go for at least a 550lb spring, depending on your riding style and local terrain. If you go for more of a poppy ride, you might want a slightly stiffer spring, or even consider an air shock as a replacement.
flag Thepureface
Posted: Dec 18, 2019 at 14:18 Quote
Whats the deal with tire inserts? Do any of you guys actually use them and of so- how come?


Are they mainly for carbon rims?
flag Beecee336
Posted: Dec 18, 2019 at 16:38 Quote
Thepureface wrote:
Whats the deal with tire inserts? Do any of you guys actually use them and of so- how come?


Are they mainly for carbon rims?

I use huck norris inserts. Super easy install and very minimal weight and cheap. I got them to protect rim dings and pinch flats. So far so good.
flag NorCalNomad
O+
Posted: Dec 18, 2019 at 17:06 Quote
Thepureface wrote:
Whats the deal with tire inserts? Do any of you guys actually use them and of so- how come?


Are they mainly for carbon rims?

Cushcore, and love them! Using them on alum rims. It's really like giving your bike more suspension and you can run lower pressures (so more traction).
flag Tripmo
Posted: Dec 18, 2019 at 17:39 Quote
Beecee336 wrote:
Thepureface wrote:
Whats the deal with tire inserts? Do any of you guys actually use them and of so- how come?


Are they mainly for carbon rims?

I use huck norris inserts. Super easy install and very minimal weight and cheap. I got them to protect rim dings and pinch flats. So far so good.

I am old school. Still running inner tubes hahaha.
I do use DH inner tubes, I do not use tire inserts. Not really see the point of having them.
flag spaceofades
O+
Posted: Dec 18, 2019 at 18:07 Quote
Thepureface wrote:
Whats the deal with tire inserts? Do any of you guys actually use them and of so- how come?


Are they mainly for carbon rims?
70% of my flats this year were the tire pinched against the rim. Next year, I will run an insert to avoid this type of flat.
flag GravityCandy
O+
Posted: Dec 21, 2019 at 18:40 Quote
I use them just to stop dinging my rim. So far mostly good.
flag NorCalNomad
O+
Posted: Dec 21, 2019 at 21:18 Quote
Tripmo wrote:

I am old school. Still running inner tubes hahaha.
I do use DH inner tubes, I do not use tire inserts. Not really see the point of having them.

You've never ridden a proper tubeless setup or one with a tire insert in it if you think that way. I was a tubeless hold out for YEARS until I got on modern tubeless.
flag fredro
Posted: Dec 21, 2019 at 22:29 Quote
What are tubes?
flag NorCalNomad
O+
Posted: Dec 21, 2019 at 22:49 Quote
fredro wrote:
What are tubes?

photo
flag deli-hustler
Posted: Dec 22, 2019 at 1:45 Quote
Something you stick inside a Tannus insert
flag Tripmo
Posted: Dec 22, 2019 at 2:50 Quote
NorCalNomad wrote:
Tripmo wrote:

I am old school. Still running inner tubes hahaha.
I do use DH inner tubes, I do not use tire inserts. Not really see the point of having them.

You've never ridden a proper tubeless setup or one with a tire insert in it if you think that way. I was a tubeless hold out for YEARS until I got on modern tubeless.

My hardtail is tubeless, but without inserts.
My DH bike is none tubeless.

Tubeless nicer you can run lower psi, but more hassle when it comes to setup.
flag Thepureface
Posted: Dec 22, 2019 at 9:05 Quote
So do the tire inserts help with keeping the tire from burping air?

Does pro core help with that?

Reason is Im a feather weight at 150lbs no gear. I can run low 20 ish psi. And get amazing traction but then my tires burp air.

Is there any tricks to keeping tires seated at low psi?

Or is it just finding a balance between not burping and getting decent traction?
flag titaniumtit
Posted: Dec 22, 2019 at 9:28 Quote
Be thankful you didn’t go plus and yes just trying and testing

Could increase by 2psi each end which will hopefully cure any burping for your low weight

 


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