Hello! Log in or Register   |  Help  |  Donate  |  Buy Shirts See all banner ads | Advertise on TheSamba.com  
TheSamba.com
 
Front end tire questions (speed/rpm's)
Forum Index -> Custom Wheel/Tire Share: Facebook Twitter
Reply to topic
Print View
Quick sort: Show newest posts on top | Show oldest posts on top View previous topic :: View next topic  
Author Message
PaytonD21
Samba Member


Joined: August 11, 2015
Posts: 83
Location: Washington, USA
PaytonD21 is offline 

PostPosted: Sun Aug 23, 2015 5:36 pm    Post subject: Front end tire questions (speed/rpm's) Reply with quote

I just purchased a 1960 beetle and am looking to put different tires on it. I plan on lowering it and want to get the correct tires now for when that happens. In the front I'm looking at 145/65-15's or 155/65-15's and on the rear I heard 205/60-15's are a good choice. I want to get a narrowed beam and drop spindles.
My question is: with the smaller tires up front how much is your speed off? And how much are your rpm's effected? I've seen many people with small tires upfront, but I would like to know how much it effects the performance of the car.
Back to top
View user's profile Send private message Gallery Classifieds Feedback
Miklo
¡Chale!


Joined: August 27, 2008
Posts: 2058
Location: Antelope Valley, Ca
Miklo is offline 

PostPosted: Mon Aug 24, 2015 1:24 pm    Post subject: Reply with quote

I am currently off by 5-7 mph with my 145/65's up front.

Rpm's are not affected by front tires.
_________________
Miklo
'55 Type1 "Ozma"
'66 Type1 "Charlotte" RIP

Antelope Valley's Mobile Air-Cooled Guru

Dr OnHolliday wrote:
As I remember it, lowriding was not one of the criteria that Adolf gave to Dr. Porsche...
Back to top
View user's profile Send private message Instagram Gallery Classifieds Feedback
PaytonD21
Samba Member


Joined: August 11, 2015
Posts: 83
Location: Washington, USA
PaytonD21 is offline 

PostPosted: Mon Aug 24, 2015 3:03 pm    Post subject: Reply with quote

I was looking at 185/65-15's for the back. Would you know how much those effect the rpm's? Can I still cruise on the freeway at decent rpm's?
Back to top
View user's profile Send private message Gallery Classifieds Feedback
easy e
Samba Member


Joined: May 28, 2008
Posts: 3930
Location: 1 hr north of Santa Barbara
easy e is offline 

PostPosted: Tue Aug 25, 2015 9:22 am    Post subject: Reply with quote

Need to know your:
4th gear
Ring gear
Desired speed
Tire diameter

Plug it into here:
http://www.crawlpedia.com/rpm_gear_calculator.htm

Maybe consider aiming for an RPM of 3,000.

I hear above 3,250 RPM = fan cavitation (fan just can't suck in air any faster, even if it spins faster) = engine gets hotter

I hear below 2,800 RPM fan isn't providing enough air for steady state freeway speed = engine getting hotter.
e
_________________
aka: Evan
Spreadsheet for Bus RPM, based on gearing & tire size (Excel format)
Searchable, click-navigable 1958 Bus Parts List
Back to top
View user's profile Send private message Instagram Gallery Classifieds Feedback
911pickup
Samba Member


Joined: March 06, 2004
Posts: 625
Location: Near Goats on the Roof
911pickup is offline 

PostPosted: Tue Aug 25, 2015 4:40 pm    Post subject: Reply with quote

There isn't much of a diameter difference between a 165/80-15, which is roughly the stock tire size, and a 185/65-15.
At 60 mph your speedo will be off by just over 2 mph (60 mph compared to 57.81 mph).
As easy e mentioned, to be precise we will need the numbers for your 4th and R&P gears.
A rough guess......probably less than a 200 rpm difference.
Back to top
View user's profile Send private message Send e-mail Gallery Classifieds Feedback
PaytonD21
Samba Member


Joined: August 11, 2015
Posts: 83
Location: Washington, USA
PaytonD21 is offline 

PostPosted: Tue Aug 25, 2015 4:54 pm    Post subject: Reply with quote

Does anyone know an easier way to find the R&P? I found out my car has a non stock transmission. I don't want to assume stock R&P.
Back to top
View user's profile Send private message Gallery Classifieds Feedback
Display posts from previous:   
Reply to topic    Forum Index -> Custom Wheel/Tire All times are Mountain Standard Time/Pacific Daylight Savings Time
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum

About | Help! | Advertise | Donate | Premium Membership | Privacy/Terms of Use | Contact Us | Site Map
Copyright © 1996-2023, Everett Barnes. All Rights Reserved.
Not affiliated with or sponsored by Volkswagen of America | Forum powered by phpBB
Links to eBay or other vendor sites may be affiliate links where the site receives compensation.